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Keywords are the words whose meaning has already been explained to the C compiler. There are only 32 keywords available in C. The keywords are also called ‘Reserved words’.

5. C Character Set

A character denotes any alphabet, digit or special symbol used to represent information. Following are the valid alphabets, numbers and special symbols allowed in C.

6. Rules for Writing, Compiling and Executing the C program

7. Data types & Placeholders

printf function will print the following:
Sum is 17
In fact %d is the placeholder for integer variable value that its name comes after double quotes.

8. Control characters (Escape sequences)

Certain non printing characters as well as the backslash () and the apostrophe('), can be expressed in terms of escape sequence.

9. Receiving input values from keyboard

scanf function used to receiving input from keyboard.
General form of scanf function is :

Format string contains placeholders for variables that we intend to receive from keyboard. A & sign comes before each variable name that comes in variable listing. Character strings are exceptions from this rule. They will not come with this sign before them.

Note: You are not allowed to insert any additional characters in format string other than placeholders and some special characters. Entering even a space or other undesired character will cause your program to work incorrectly and the results will be unexpected. So make sure you just insert placeholder characters in scanf format string. The following example receives multiple variables from keyboard.

Pay attention that scanf function has no error checking capabilities built in it. Programmer is responsible for validating input data (type, range etc.) and preventing errors

Expression & Operators Precedence - C Programming

Following table summaries the rules for precedence and associativity of all operators, including those that we have not yet discussed. Operators on the same row have the same precedence; rows are in order of decreasing precedence, so, for example, *, /, and % all have the same precedence, which is higher than that of binary + and -. The operator () refers to function call. The operators -> and . are used to access members of structures;

The Decision Control Structure - C Programming

DESCRIPTION	OPERATORS	ASSOCIATIVITY
Function Expression	()	Left to Right
Array Expression	[]	Left to Right
Structure Operator	->	Left to Right
Structure Operator	.	Left to Right
Unary minus	-	Right to Left
Increment/Decrement	++, --	Right to Left
One’s compliment	~	Right to Left
Negation	!	Right to Left
Address of	&	Right to Left
Value of address	`*`	Right to Left
Type cast	(type)	Right to Left
Size in bytes	sizeof	Right to Left
Multiplication	`*`	Left to Right
Division	/	Left to Right
Modulus	%	Left to Right
Addition	+	Left to Right
Subtraction	-	Left to Right
Left shift	<<	Left to Right
Right shift	>>	Left to Right
Less than	<	Left to Right
Less than or equal to	<=	Left to Right
Greater than	>	Left to Right
Greater than or equal to	>=	Left to Right
Equal to	==	Left to Right
Not equal to	!=	Left to Right
Bitwise AND	&	Left to Right
Bitwise exclusive OR	^	Left to Right
Bitwise inclusive OR	\|	Left to Right
Logical AND	&&	Left to Right
Logical OR	\|\|	Left to Right
Conditional	?:	Right to Left
Assignment	=, *=, /=, %=, +=, -=, &=, ^=, \|=, <<=, >>=	Right to Left
Comma	,	Right to Left

C has three major decision making instructions—the if statement, the if-else statement, and the switch statement.

1. The if Statement

C uses the keyword if to implement the decision control instruction. The general form of if statement looks like this:

Here the expression can be any valid expression including a relational expression. We can even use arithmetic expressions in the ifstatement. For example all the following if statements are valid

The expression (3 + 2 % 5) evaluates to 5 and since 5 is non-zero it is considered to be true. Hence the printf("This works"); gets executed.

2. The if-else Statement

The if statement by itself will execute a single statement, or a group of statements, when the expression following if evaluates to true. It does nothing when the expression evaluates to false. Can we execute one group of statements if the expression evaluates to true and another group of statements ifthe expression evaluates to false? Of course! This is what is the purpose of the else statement that is demonstrated as

3. Nested if-elses

If we write an entire if-else construct within either the body of the if statement or the body of an else statement. This is called "nesting" of ifs. This is demonstrated as -

4. The if-else Ladder/else-if Clause

The expressions are evaluated in order; if an expressionis true, the "statement" or "block of statement" associated with it is executed, and this terminates the whole chain. As always, the code for each statement is either a single statement, or a group of them in braces. The last else part handles the "none of the above" or default case where none of the other conditions is satisfied.

5. Switch Statements or Control Statements

The switch statement is a multi-way decision that tests whether an expression matches one of a number of constant integer values, and branches accordingly. The switch statement that allows us to make a decision from the number of choices is called a switch, or more correctlya switch-case-default, since these three keywords go together to make up the switch statement.

6. switch Versus if-else Ladder

The Loop Control Structure - C Programming

Sometimes we want some part of our code to be executed more than once. We can either repeat the code in our program or use loops instead. It is obvious that if for example we need to execute some part of code for a hundred times it is not practical to repeat the code. Alternatively we can use ourrepeating code inside a loop.

There are three methods for, while and do-while which we can repeat a part of a program.

1. while loop

while loop is constructed of a condition or expression and a single command or a block of commands that must run
in a loop.

The statements within the while loopwould keep on getting executed till the condition being tested remains true. When the condition becomes false, the control passes to the first statement that follows the body of the while loop.

Example

When the above code is compiled and executed, it produces the following result −

2. for loop

for loop is something similar to while loop but it is more complex. for loop is constructed from acontrol statement that determines how many times the loop will run and a command section. Command section is either a single command or a block of commands.

Example

When the above code is compiled and executed, it produces the following result −

3. do-while loop

The while and for loops test the termination condition at the top. By contrast, the third loop in C, the do-while, tests at the bottom after making each pass through the loop body; the body is always executed at least once.
The syntax of the do is

The statement is executed, then expression is evaluated. If it is true, statement is evaluated again, and so on. When the expression becomes false, the loop terminates. Experience shows that do-while is much less used than while and for. A do-whileloop is used to ensure that the statements within the loop are executed at least once.

Example

When the above code is compiled and executed, it produces the following result −

4. Break and Continue statement

We used break statement in switch...case structures in previouslly. We can also use
"break" statement inside loops to terminate a loop and exit it (with a specific condition).

In above example loop execution continues until either num>=20 or entered score is negative.

Continue statement can be used in loops. Like breakcommand continue changes flow of a program. It does not terminate the loop however. It just skips the rest of current iteration of the loop and returns to starting point of the loop.

Example 1 (break)

When the above code is compiled and executed, it produces the following result −

Example 2 (continue)

In above example, program accepts all input but omits the '.' character from it. The text will be echoed as you enter it but the main output will be printed after you press the enter key (which is equal to inserting a "\n" character) is pressed. As we told earlier this is because getchar() function is a buffered input function.

5. Goto and labels

C provides the infinitely-abusable goto statement, and labels to branch to. Formally, the goto statement is never necessary, and in practice it is almost always easy to write code without it. We have not used goto in this book.

Nevertheless, there are a few situations where gotos may find a place. The most common is to abandon processing in some deeply nested structure, such as breaking out of two or more loops at once. The break statement cannot be used directly since it only exits from the innermost loop. Thus:

This organization is handy if the error-handling code is non-trivial, and if errors can occur in several places.

A label has the same form as a variable name, and is followed by a colon. It can be attached to any statement in the same function as the goto. The scope of a label is the entire function.

Example

When the above code is compiled and executed, it produces the following result −

Note - By uses of goto, programs become unreliable, unreadable, and hard to debug. And yet many programmers find goto seductive.

Array - C Programming

Arrays are structures that hold multiple variables of the same data type. The first element in the array is numbered 0, so the last element is 1 less than the size of the array. An array is also known as a subscripted variable. Before using an array its type and dimension must be declared.

1. Array Declaration

Like other variables an array needs to be declared so that the compiler will know what kind of an array and how large an array we want.

Here, int specifies the type of the variable, just as it does with ordinary variables and the word marks specifies the name of the variable. The [30] however is new. The number 30 tells how many elements of the type int will be in our array. This number is often called the "dimension" of the array. The bracket ( [ ] ) tells the compiler that we are dealing with an array.

Let us now see how to initialize an array while declaring it. Following are a few examples that demonstrate this.

2. Accessing Elements of an Array

Once an array is declared, let us see how individual elements in the array can be referred. This is done with subscript, the number in the brackets following the array name. This number specifies the element’s position in the array. All the array elements are numbered, starting with 0. Thus, marks [2] is not the second element of the array, but the third.

3. Entering Data into an Array

The for loop causes the process of asking for and receiving a student’s marks from the user to be repeated 30 times. The first time through the loop, i has a value 0, so the scanf() function will cause the value typed to be stored in the array element marks[0], the first element of the array. This process will be repeated until i becomes 29. This is last time through the loop, which is a good thing, because there is no array element like marks[30].

In scanf() function, we have used the "address of" operator (&) on the element marks[i] of the array. In so doing, we are passing the address of this particular array element to the scanf() function, rather than its value; which is what scanf() requires.

4. Reading Data from an Array

The balance of the program reads the data back out of the array and uses it to calculate the average. The for loop is much the same, but now the body of the loop causes each student’s marks to be added to a running total stored in a variable called sum. When all the marks have been added up, the result is divided by 30, the number of students, to get the average.

5. Advantages of using an Array

6. Disadvantages of using an Array

7. Multidimensional arrays

The simplest form of multidimensional array is the two-dimensional array. A two-dimensional array is, in essence, a list of one-dimensional arrays. To declare a two-dimensional integer array of size [x][y], you would write something as follows −

Multidimensional arrays may be initialized by specifying bracketed values for each row. Following is an array with 3 rows and each row has 4 columns.

The nested braces, which indicate the intended row, are optional. The following initialization is equivalent to the previous example −

8. Example

8.1 Simple Array

Let us try to write a program to find average marks obtained by a
class of 30 students in a test.

8.2 Two-Dimensional Array

1. What is a Function?

EXAMPLE STATEMENT FOR STRING IN C LANGUAGE
1. Check whether two strings are anagrams or not /***************************************************** Statement - Check whether two strings are anagrams or not Programmer - Vineet Choudhary Written For - http://developerinsider.co ****************************************************/ / What is anagrams? Two words are said to be anagrams of each other if the letters from one word can be rearranged to form the other word. From the above definition it is clear that two strings are anagrams if all characters in both strings occur same number of times. For example "abc" and "cab" are anagram strings, here every character 'a', 'b' and 'c' occur only one time in both strings */ #include <stdio.h> int check_anagram(char [], char []); void main() { char a[100], b[100]; int flag; clrscr(); printf("Enter first string\n"); gets(a); printf("Enter second string\n"); gets(b); flag = check_anagram(a, b); if (flag == 1) printf("\"%s\" and \"%s\" are anagrams.\n", a, b); else printf("\"%s\" and \"%s\" are not anagrams.\n", a, b); getch(); } int check_anagram(char a[], char b[]) { int first[26] = {0}, second[26] = {0}, c = 0; while (a[c] != '\0') { first[a[c]-'a']++; c++; } c = 0; while (b[c] != '\0') { second[b[c]-'a']++; c++; } for (c = 0; c < 26; c++) { if (first[c] != second[c]) return 0; } return 1; }
2. Find a frequenct of character in string /***************************************************** Statement - Find a frequenct of character in string Programmer - Vineet Choudhary Written For - http://developerinsider.co *****************************************************/ #include <stdio.h> #include <string.h> #include <conio.h> void find_frequency(char [], int []); void main() { char string[100]; int c, count[26] = {0}; clrscr(); printf("Input a string\n"); gets(string); find_frequency(string, count); printf("Character Count\n"); for (c = 0 ; c < 26 ; c++) { printf("%c \t %d\n", c + 'a', count[c]); } getch(); } void find_frequency(char s[], int count[]) { int c = 0; while (s[c] != '\0') { if (s[c] >= 'a' && s[c] <= 'z' ) count[s[c]-'a']++; c++; } }
3. Insert substring into a string /***************************************************** Statement - Insert substring into a string Programmer - Vineet Choudhary Written For - http://developerinsider.co ****************************************************/ #include <stdio.h> #include <conio.h> #include <string.h> #include <stdlib.h> void insert_substring(char, char, int); char substring(char, int, int); void main() { char text[100], substring[100]; int position; clrscr(); printf("Enter some text\n"); gets(text); printf("Enter the string to insert\n"); gets(substring); printf("Enter the position to insert\n"); scanf("%d", &position); insert_substring(text, substring, position); printf("%s\n",text); getch(); } void insert_substring(char a, char b, int position) { char f, e; int length; length = strlen(a); f = substring(a, 1, position - 1 ); e = substring(a, position, length-position+1); strcpy(a, ""); strcat(a, f); free(f); strcat(a, b); strcat(a, e); free(e); } char substring(char string, int position, int length) { char pointer; int c; pointer = malloc(length+1); if( pointer == NULL ) exit(EXIT_FAILURE); for( c = 0 ; c < length ; c++ ) (pointer+c) = ((string+position-1)+c); *(pointer+c) = '\0'; return pointer; }
4. Substring from a position to length /***************************************************** Statement - Substring from a position to length Programmer - Vineet Choudhary Written For - http://developerinsider.co *****************************************************/ #include <stdio.h> #include <conio.h> void main() { char string[1000], sub[1000]; int position, length, c = 0; clrscr(); printf("Input a string\n"); gets(string); printf("Enter the position and length of substring\n"); scanf("%d%d", &position, &length); while (c < length) { sub[c] = string[position+c-1]; c++; } sub[c] = '\0'; printf("Required substring is \"%s\"\n", sub); getch(); }
5. Check if a string is a subsequence of another string /******************************************************** Statement - check if a string is a subsequence of another string Programmer - Vineet Choudhary Written For - http://developerinsider.co *******************************************************/ / C program to check Subsequence, don't confuse subsequence with substring. In our program we check if a string is a subsequence of another string. User will input two strings and we find if one of the strings is a subsequence of other. Program prints yes if either first string is a subsequence of second or second is a subsequence of first. We pass smaller length string first because our function assumes first string is of smaller or equal length than the second string. / #include <stdio.h> #include <string.h> #include <conio.h> int check_subsequence (char [], char[]); void main () { int flag; char s1[1000], s2[1000]; clrscr(); printf("Input first string\n"); gets(s1); printf("Input second string\n"); gets(s2); /* Passing smaller length string first / if (strlen(s1) < strlen(s2)) flag = check_subsequence(s1, s2); else flag = check_subsequence(s2, s1); (flag)?printf("YES\n"):printf("NO\n"); getch(); } int check_subsequence (char a[], char b[]) { int c, d; c = d = 0; while (a[c] != '\0') { while ((a[c] != b[d]) && b[d] != '\0') { d++; } if (b[d] == '\0') break; d++; c++; } if (a[c] == '\0') return 1; else return 0; } / The logic of function is simple we keep on comparing characters of two strings, if mismatch occur then we move to next character of second string and if characters match indexes of both strings is increased by one and so on. If the first string ends then it is a subsequence otherwise not. */
6. Delete vowels from a string

A function is combined of a block of code that can be called or used anywhere in the program by calling the name. Body of a function starts with { and ends with } . This is similar to the main function. Example below shows how we can write a simple function.

In above example we have put a section of program in a separate function. Function body can be very complex though. After creating a function we can call it using its name. Functions can also call each other. A function can even call itself.

By the way pay attention to function prototypes section. In some C compilers we are needed to introduce the functions we are creating in a program above the program. Introducing a function is being called function prototype.

2. Why Use Functions

Why write separate functions at all? Why not squeeze the entire
logic into one function, main()? Two reasons:

What is the moral of the story? Don’t try to cram the entire logic in one function. It is a very bad style of programming. Instead, break a program into small units and write functions for each of these isolated subdivisions. Don’t hesitate to write functions that are called only once. What is important is that these functions perform some logically isolated task.

3. Function arguments

Functions are able to accept input parameters in the form of variables. These input parameter variables
can then be used in function body.

In above example we have called sayhello() function with the parameter 4. This function receives an input value and assigns it to count variable before starting execution of function body. sayhello() function will then print a hello message count times on the screen.

4. Function return values

In mathematics we generally expect a function to return a value. It may or may not accept arguments but it always returns a value.

This return value has a type as other values in C. It can be int, float, char or anything else. Type of this return value determines type of your function.

Default type of function is int or integer. If you do not indicate type of function that you use, it will be of type int. As we told earlier every function must return a value. We do this with return command.

Above function returns the value of variable c as the return value of function. We can also use expressions in return command. For example we can replace two last lines of function with return a+b; If you forget to return a value in a function you will get a warning message in most of C compilers. This message will warn you that your function must return a value. Warnings do not stop program execution but errors stop it.

In our previous examples we did not return any value in our functions. For example you must return a value in main() function.

Default return value for an int type function is 0. If you do not insert return 0 or any other value in your main() function a 0 value will be returned automatically. If you are planning to return an int value in your function, it is seriously preferred to mention the return value in your function header and make.

5. void return value

There is another void type of function in C language. Void type function is a function that does not return a value. You can define a function that does not need a return value as void.

void functions cannot be assigned to a variable because it does not return value. So you cannot write:

6. Recursive Function

In C, it is possible for the functions to call themselves. A function is called recursive if a statement within the body of a function calls the same function.

Foxed? Well, that is recursion for you in its simplest garbs. I hope you agree that it’s difficult to visualize how the control flows from one function call to another. Possibly Following figure would make things a bit clearer.

7. Multiple Parameters

In fact you can use more than one argument in a function. Following example will show you how you can do this.

8. Call by value

C programming language function calls, use call by value method. Let’s see an example to understand this subject better.

In main() function, we have declared a variable m. We have assigned value 2 to m. We want to see if function call is able to change value of m as we have modified value of incoming parameter inside test() function.

So you see function call has not changed the value of argument. This s is because function-calling method only sends value of variable m to the function and it does not send variable itself. Actuallyit places value of variable m in a memory location called stack and then function retrieves the value without having access to main variable itself. This is why we call this method of calling "call by value".

9. Call by reference

There is another method of sending variables being called "Call by reference". This second method enables function to modify value of argument variables used in function call.

To be able to modify the value of a variable used as an argument in a function, function needs to know memory address of the variable (where exactly the variable is situated in memory).

In C programming language & operator gives the address at which the variable is stored. For example if m is a variable of type int then &m will give us the starting memory address of our variable.We call this resulting address a pointer.

In above command ptr variable will contain memory address of variable m. This method is used in some of standard functions in C. For example scanf function uses this method to be able to receive values from console keyboard and put it in a variable. In fact it places received value in memory location of the variable used in function. Now we understand the reason why we add & sign before variable names in scanf variables.

Now that we have memory address of variable we must use an operator that enables us to assign a value or access to value stored in that address.

Let’s look at our example again. We have passed pointer (memory address) to function. Now function is able to modify value stored inside variable. If yourun the program, you will get these results:

So you see this time we have changed value of an argument variable inside the called function (by modifying the value inside the memory location of our main variable).

Pointers - C Programming

1. What is a Pointer?

A pointer is a variable that contains the address of a variable. The main thing is that once you can talk about the address of a variable, you'll then be able to goto that address and retrieve the data stored in it.

2. C Pointer Syntax

Pointers require a bit of new syntax because when you have a pointer, you need the ability to both request the memory location it stores and the value stored at that memory location. Moreover, since pointers are some what special, you need to tell the compiler when you declare your pointer variable that the variable is a pointer, and tell the compiler what type of memory it points to.

For example, you could declarea pointer that stores the address of an integer with the following syntax:

Notice the use of the *. This is the key to declaring a pointer; if you add it directly before the variable name, it will declare the variable to be a pointer.

3. Pointer Notation

We see that the computer has selected memory location 65524 as the place to store the value 3. The location number 65524 is not a number to be relied upon, because some other time the computer may choose a different location for storing the value 3. The important point is, i’s address in memory is a number. We can print this address number through the following program:

Look at the first printf() statement carefully. & used in this statement is C’s "address of" operator. The expression &i returns the address of the variable i, which in this case happens to be 65524. Since 65524 represents an address, there is no question of a sign being associated with it. Hence it is printed out using %u, which is a format specifier for printing an unsigned integer. We have been using the & operator all the time in the scanf() statement.

The other pointer operator available in C is *, called "value at address" operator. It gives the value stored at a particular address. The "value at address" operator is also called "indirection" operator.

Note that printing the value of *(&i) is same as printing the value of i. The expression &i gives the address of the variable i. This address can be collected in a variable, by saying,

But remember that j is not an ordinary variable like any other integer variable. It is a variable that contains the address of other variable (i in this case). Since j is a variable the compiler must provide it space in the memory. Once again, the following memory map would illustrate the contents of i and j.

As you can see, i's value is 3 and j's value is i's address. But wait, we can’t use j in a program without declaring it. And since j is a variable that contains the address of i, it is declared as,

This declaration tells the compiler that j will be used to store the address of an integer value. In other words j points to an integer. How do we justify the usage of * in the declaration,

Let us go by the meaning of *. It stands for "value at address". Thus, int *j would mean, the value at the address contained in j is an int.

4. Example

5. Examples

A structure is a collection of one or more variables, possibly of different types, grouped together under a single name for convenient handling.

1. Declaring a Structure

Once the new structure data type has been defined one or more variables can be declared to be of that type.

EXAMPLE STATEMENT FOR POINTER IN C LANGUAGE
1. Add numbers using call by reference /***************************************************** Statement - Add numbers using call by reference Programmer - Vineet Choudhary Written For - http://developerinsider.co ****************************************************/ #include <stdio.h> #include <conio.h> long add(long , long ); void main() { long first, second, sum; clrscr(); printf("Input two integers to add\n"); scanf("%ld%ld", &first, &second); sum = add(&first, &second); printf("(%ld) + (%ld) = (%ld)\n", first, second, sum); getch(); } long add(long x, long y) { long sum; sum = x + *y; return sum; }
2. Multilevel Pointer [With Explanation] /******************************************************** Statement - Multilevel Pointer [With Explanation] Programmer - Vineet Choudhary Written For - http://developerinsider.co *******************************************************/ #include<stdio.h> #include<conio.h> void main(){ int s=2,r=&s,q=&r,p=&q; clrscr(); printf("%d",p[0][0][0]); getch(); } / Multilevel Pointer ------------------- A pointer is pointer to another pointer which can be pointer to others pointers and so on is known as multilevel pointers. We can have any level of pointers. Explanation ------------- As we know p[i] =(p+i) So, P[0][0][0]=(p[0][0]+0)=p[0]=p Another rule is: &i=i So, *p=* (&q) =q= (&r) =r=(&s) =s=2 */
3. Sum of array elements using pointers

For example the variables b1, b2, b3 can be declared to be of the type struct book,

This statement sets aside space in memory. It makes available space to hold all the elements in the structure—in this case, 7 bytes — one for name, four for price and two for pages. These bytes are always in adjacent memory locations.

Like primary variables and arrays, structure variables can also be initialized where they are declared. The format used is quite similar to that used to initiate arrays.

2. Accessing Structure Elements

In arrays we can access individual elements of an array using a subscript. Structures use a different scheme. They use a dot (.) operator. So to refer to pages of the structure defined in book structure we have to use,

Note that before the dot there must always be a structure variable and after the dot there must always be a structure element.

3. Example

4. Structures as Function Arguments

You can pass a structure as a function argument in the same way as you pass any other variable.

When the above code is compiled and executed, it produces the following result −

5. Summary

6. Examples

Files Handling - C Programming

1. File Pointers

There are many ways to use files in C. The most straight forward use of files is via a file pointer.

EXAMPLE STATEMENT FOR STRUCTURE AND UNION IN C LANGUAGE
1. Calculate Size of Structure
/******************************************************** Statement - Calculate Size of Structure Programmer - Vineet Choudhary Written For - http://developerinsider.co *******************************************************/ #include<stdio.h> struct stud { int roll; char name[10]; int marks; }; int main() { int size; struct stud s; size = sizeof(s); printf("nSize of Structure : %d", size); return(0); } / Explanation : --------------- Structure is Collection of elements of the Different data Types. Size of the Structure Can be Evaluated using “sizeof Operator” size = sizeof(s); Formula for Calculating Size of Structure : ------------------------------------------- Size of Structure 'S' = sizeof(roll) + sizeof(name) + sizeof(mark) = 2 + 10 + 2 = 14 ->Size depends on your computer Remember : ---------- sizeof is Operator not function sizeof Operator Takes any Variable as Parameter. / 2. Use structure within union*
/******************************************************** Statement - Use structure within union Programmer - Vineet Choudhary Written For - http://developerinsider.co ******************************************************/ #include<stdio.h> #include<conio.h> void main() { struct student { char name[30]; char sex; int rollno; float percentage; }; union details { struct student st; }; union details set; clrscr(); printf("Enter details:"); printf("\nEnter name : "); scanf("%s", set.st.name); printf("\nEnter roll no : "); scanf("%d", &set.st.rollno); flushall(); printf("\nEnter sex : "); scanf("%c", &set.st.sex); printf("\nEnter percentage :"); scanf("%f", &set.st.percentage); printf("\nThe student details are : \n"); printf("\name : %s", set.st.name); printf("\nRollno : %d", set.st.rollno); printf("\nSex : %c", set.st.sex); printf("\nPercentage : %f", set.st.percentage); getch(); } 3. Find the size of a union**

The type FILE, is not a basic type, instead it is defined in the header file stdio.h, this file must be included in your program.

2. Opening a File

The following useful table from the ANSI C Rationale lists the different actions and requirements of the different modes for opening a file:

fopen returns NULL if the file could not be opened in the mode requested. The returned value should be checked before any attempt is made to access the file. The following code shows how the value returned by fopen might be checked. When the file cannot be opened a suitable error message is printed and the program halted. In most situations this would be inappropriate, instead the user should be given the chance of re-entering the file name.

The standard header file stdio.h defines three file pointer constants, stdin ,stdout and stderr for the standard input, output and error streams. It is considered good practice to write error messages to the standard error stream.

The functions fscanf() and getc() are used for sequential access to the file, that is subsequent reads will read the data following the data just read, and eventually you will reach the end of the file. If you want to move forwards and backwards through the file, or jump to a specific offset from the beginning, end or current location use the fseek() function (though the file mustbe opened in binary mode). The function ftell() reports the current offset from the beginning of the file.

If you wish to mix reading and writing to the same file, each switch from reading to writing (or vice versa) mustbe preceded by a call to fseek(), fsetpos(), rewind() or fflush(). If it is required to stay at the same position in the file then use fflush() or fseek(fp,0L,SEEK_CUR) which will move 0 bytes from the current position!

3. Examples

EXAMPLE STATEMENT FOR FILES HANDLING IN C LANGUAGE
1. Illustrate as to how the data stored on the disk is read /******************************************************** Statement - Illustrate as to how the data stored on the disk is read Programmer - Vineet Choudhary Written For - http://developerinsider.co *******************************************************/ #include <stdio.h> #include <stdlib.h> #include <conio.h> void main() { FILE fptr; char filename[15]; char ch; clrscr(); printf("Enter the filename to be opened\n"); gets(filename); fptr = fopen (filename, "r"); /open for reading/ if (fptr == NULL) { printf("Cannot open file\n"); exit(0); } ch = fgetc(fptr); while (ch != EOF) { printf ("%c", ch); ch = fgetc(fptr); } fclose(fptr); getch(); } /* End of main () / /---------------------------------------------- Output Enter the filename to be opened emp.rec Name = Prabhu Age = 25 Salary = 25000.00 ------------------------------------------------*/
2. Write static data in file and read from file

he arguments that we pass on to main() at the command prompt are called command line arguments. The full declaration of main looks like this:

The function main() can have two arguments, traditionally named as argc and argv. Out of these, argv is an array of pointers to strings and argc is an int whose value is equal to the number of strings to which argv points. When the program is executed, the strings on the command line are passed to main(). More precisely, the strings at the command line are stored in memory and address of the first string is stored in argv[0], address of the second string is stored in argv[1] and so on. The argument argc is set to the number of strings given on the command line.

For example

Following is a simple example which checks if there is any argument supplied from the command line and take action accordingly −

When the above code is compiled and executed with single argument, it produces the following result.

Results of Parsing Command Lines

The following table shows example input and expected output, demonstrating the rules in the preceding list.

Type Casting - C Programming

Type casting refers to changing an variable of one data type into another. The compiler will automatically change one type of data into another if it makes sense. For instance, if you assign an integer value to a floating-point variable, the compiler will convert the int to a float. Casting allows you to make this type conversion explicit, or to force it when it wouldn’t normally happen.

1. Implicit Type Conversion

When the type conversion is performed automatically by the compiler without programmers intervention, such type of conversion is known as implicit type conversion or type promotion.

2. Explicit Type Conversion

The type conversion performed by the programmer by posing the data type of the expression of specific type is known as explicit type conversion. The explicit type conversion is also known as type casting.

where, data_type is any valid c data type, and expression may be constant, variable or expression.

The following rules have to be followed while converting the expression from one type to another to avoid the loss of information:

Example

If we want to get the exact value of 7/5 then we need explicit casting from int to float:

Storage class specifiers are the keywords which can appear next to the top-level type of a declaration. The use of these keywords affects the storage duration and linkage of the declared object, depending on whether it is declared at file scope or at block scope:

1. auto

This storage class denotes that an identifier has automatic storage duration. This means once the scope in which the identifier was defined ends, the object denoted by the identifier is no longer valid.

Since all objects, not living in global scope or being declared static, have automatic storage duration by default when defined, this keyword is mostly of historical interest and should not be used:

2. register

Hints to the compiler that access to an object should be as fast as possible. The register storage class is more appropriate for variables that are defined inside a block and are accessed with high frequency. For example,

COMMAND-LINE INPUT	ARGV[1]	ARGV[2]	ARGV[3]
"abc" d e	abc	d	e
a\\b d"e f"g h	a\\b	de fg	h
a\\\"b c d	a\"b	c	d
a\\\\"b c" d e	a\\b c	d	e

In C11, The _Alignof operator is also allowed to be used with register arrays.

3. extern

Used to declare an object or function that is defined elsewhere (and that has external linkage). In general, it is used to declare an object or function to be used in a module that is not the one in which the corresponding object or function is defined:

Things get slightly more interesting with the introduction of the inline keyword in C99:

Hints to the compiler that the function bar might be inlined and suppresses the generation of an external symbol, unless stated otherwise.

To be found in just one .c file. Creates an external function definition of bar for use by other files. The compiler is allowed to choose between the inline version and the external definition when bar is called. Without this line, bar would only be an inline function, and other files would not be able to call it.

4. static

The static storage class serves different purposes, depending on the location of the declaration in the file:

5. ___Thread_local

This was a new storage specifier introduced in C11 along with multi-threading. This isn't available in earlier C standards.

Denotes thread storage duration. A variable declared with _Thread_local storage specifier denotes that the object is local to that thread and its lifetime is the entire execution of the thread in which it's created. It can also appear along with static or extern.

6. typedef

Defines a new type based on an existing type. Its syntax mirrors that of a variable declaration.

While not technically a storage class, a compiler will treat it as one since none of the other storage classes are allowed if the typedef keyword is used.

Preprocessor Directives - C Programming

The C preprocessor is a macro processor that is used automatically by the C compiler to transform your program before actual compilation (Proprocessor direcives are executed before compilation.). It is called a macro processor because it allows you to define macros, which are brief abbreviations for longer constructs. A macro is a segment of code which is replaced by the value of macro. Macro is defined by #define directive.

Preprocessing directives are lines in your program that start with #. The # is followed by an identifier that is the directive name. For example, #define is the directive that defines a macro. Whitespace is also allowed before and after the #.

The # and the directive name cannot come from a macro expansion. For example, if foo is defined as a macro expanding to define, that does not make #foo a valid preprocessing directive.

List of preprocessor directives :

1. #include

The #include preprocessor directive is used to paste code of given file into current file. It is used include system-defined and user-defined header files. If included file is not found, compiler renders error. It has three variants:

#include <file>

This variant is used for system header files. It searches for a file named file in a list of directories specified by you, then in a standard list of system directories.

#include "file"

This variant is used for header files of your own program. It searches for a file named file first in the current directory, then in the same directories used for system header files. The current directory is the directory of the current input file.

#include anything else

This variant is called a computed #include. Any #include directive whose argument does not fit the above two forms is a computed include.

2. Macro's (#define)

Let's start with macro, as we discuss, a macro is a segment of code which is replaced by the value of macro. Macro is defined by #define directive.

1. Object-like Macros

The object-like macro is an identifier that is replaced by value. It is widely used to represent numeric constants. For example:

Here, PI is the macro name which will be replaced by the value 3.14. Let's see an example of Object-like Macros :

2. Function-like Macros

Preprocessor Formatting

A preprocessing directive cannot be more than one line in normal circumstances. It may be split cosmetically with Backslash-Newline. Comments containing Newlines can also divide the directive into multiple lines.

3. #undef

To undefine a macro means to cancel its definition. This is done with the #undef directive.

4. #ifdef

The #ifdef preprocessor directive checks if macro is defined by #define. If yes, it executes the code.

5. #ifndef

The #ifndef preprocessor directive checks if macro is not defined by #define. If yes, it executes the code.

6. #if

The #if preprocessor directive evaluates the expression or condition. If condition is true, it executes the code.

7. #else

The #else preprocessor directive evaluates the expression or condition if condition of #if is false. It can be used with #if, #elif, #ifdef and #ifndef directives.

8. #error

The #error preprocessor directive indicates error. The compiler gives fatal error if #error directive is found and skips further compilation process.

9. #pragma

The #pragma preprocessor directive is used to provide additional information to the compiler. The #pragma directive is used by the compiler to offer machine or operating-system feature. Different compilers can provide different usage of #pragma directive.

An assertion is a statement used to assert that a fact must be true when that line of code is reached. Assertions are useful for ensuring that expected conditions are met.

1. Simple Assertion

Simple assertion can be implemented using assert(expression) method of assert.h header file.
Syntax

When the condition passed to an assertion is true, there is no action. The behaviour on false conditions depends on compiler flags. When assertions are enabled, a false input causes an immediate program halt. When they are disabled, no action is taken. It is common practice to enable assertions in internal and debug builds, and disable them in release builds, though assertions are often enabled in release (Whether termination is better or worse than errors depends on the program.)

Assertions should be used only to catch internal programming errors, which usually means being passed bad parameters.

Example

2. Static Assertions (C11)

Static assertions are used to check if a condition is true when the code is compiled. If it isn't, the compiler is required to issue an error message and stop the compiling process.

A static assertion is one that is checked at compile time, not run time. The condition must be a constant expression, and if false will result in a compiler error. The first argument, the condition that is checked, must be a constant expression, and the second a string literal.

Unlike assert, _Static_assert is a keyword. A convenience macro static_assert is also defined in assert.h header file. Static assertion only available in C11 version of C..

Example

3. Trick to display error message in Simple Assertion

A trick exists that can display an error message along with an assertion. Normally, you would write code like this

The reason as to why this works is that a string literal always evaluates to non-zero (true). Adding && 1 to a Boolean expression has no effect. Thus, adding && "error message" has no effect either, except that the compiler will display the entire expression that failed.

Graphics (graphics.h) - C Programming

Graphics programming in C used to drawing various geometrical shapes(rectangle, circle eclipse etc), use of mathematical function in drawing curves, coloring an object with different colors and patterns and simple animation programs like jumping ball and moving cars.

1. First graphics program (Draw a line)

#include<graphics.h>
#include<stdio.h>
#include<conio.h>

void main(void) {
    int gdriver = DETECT, gmode;
    int x1 = 200, y1 = 200;
    int x2 = 300, y2 = 300;
    clrscr();
    
    initgraph(&gdriver, &gmode, "c:\\turboc3\\bgi");
    line(x1, y1, x2, y2);
    getch();
    closegraph();
}

2. Explanation of Code :

The first step in any graphics program is to include graphics.h header file. The graphics.h header file provides access to a simple graphics library that makes it possible to draw lines, rectangles, ovals, arcs, polygons, images, and strings on a graphical window.

The second step is initialize the graphics drivers on the computer using initgraph method of graphics.h library.

void initgraph(int *graphicsDriver, int *graphicsMode, char *driverDirectoryPath);

It initializes the graphics system by loading the passed graphics driver then changing the system into graphics mode. It also resets or initializes all graphics settings like color, palette, current position etc, to their default values. Below is the description of input parameters of initgraph function.

graphicsDriver : It is a pointer to an integer specifying the graphics driver to be used. It tells the compiler that what graphics driver to use or to automatically detect the drive. In all our programs we will use DETECT macro of graphics.h library that instruct compiler for auto detection of graphics driver.
graphicsMode : It is a pointer to an integer that specifies the graphics mode to be used. If *gdriver is set to DETECT, then initgraph sets *gmode to the highest resolution available for the detected driver.
driverDirectoryPath : It specifies the directory path where graphics driver files (BGI files) are located. If directory path is not provided, then it will search for driver files in current working directory directory. In all our sample graphics programs, you have to change path of BGI directory accordingly where you Turbo C++ compiler is installed.

We have declared variables so that we can keep track of starting and ending point.

int x1=200, y1=200;
int x2=300, y2=300;

No, We need to pass just 4 parameters to the line function.

line(x1,y1,x2,y2);

line Function Draws Line From (x1,y1) to (x2,y2) .

Syntax : line(x1,y1,x2,y2);

Parameter Explanation

x1 - X Co-ordinate of First Point
y1 - Y Co-ordinate of First Point
x2 - X Co-ordinate of Second Point
y2 - Y Co-ordinate of Second Point

At the end of our graphics program, we have to unloads the graphics drivers and sets the screen back to text mode by calling closegraph function.

3. Colors in C Graphics Programming

There are 16 colors declared in graphics.h header file. We use colors to set the current drawing color, change the color of background, change the color of text, to color a closed shape etc (Foreground and Background Color). To specify a color, we can either use color constants like setcolor(RED), or their corresponding integer codes like setcolor(4). Below is the color code in increasing order.

CONSTANT	VALUE	BACKGROUND?	FOREGROUND?
BLACK	0	Yes	Yes
BLUE	1	Yes	Yes
GREEN	2	Yes	Yes
CYAN	3	Yes	Yes
RED	4	Yes	Yes
MAGENTA	5	Yes	Yes
BROWN	6	Yes	Yes
LIGHTGRAY	7	Yes	Yes
DARKGRAY	8	NO	Yes
LIGHTBLUE	9	NO	Yes
LIGHTGREEN	10	NO	Yes
LIGHTCYAN	11	NO	Yes
LIGHTRED	12	NO	Yes
LIGHTMAGENTA	13	NO	Yes
YELLOW	14	NO	Yes
WHITE	15	NO	Yes
BLINK	128	NO	*

***** To display blinking characters in text mode, add BLINK to the foreground color. (Defined in conio.h)

4. Graphics example using color

//Include the graphics header file
#include<graphics.h>
#include<stdio.h>
#include<conio.h>
 
void main()
{
   //Initialize the variables for the graphics driver and mode
   int gd = DETECT, gm;
   clrscr();
   initgraph(&gd, &gm, "C:\\TURBOC3\\BGI");

   //Set the color of the object you want to draw. 
   setcolor(BLUE);

   //Draw an object. For this example,drawing a rectangle using the rectangle function
   rectangle(50,50,100,100);

   getch();

   //unloads the graphics drivers
   closegraph();
}

5. Examples

EXAMPLE STATEMENT FOR GRAPHICS IN C LANGUAGE

EXAMPLE STATEMENT FOR GRAPHICS IN C LANGUAGE
1. Drawing Line in Graphics Mode
/******************************************** Statement - Drawing Line in Graphics Mode Programmer - Vineet Choudhary Written For - http://developerinsider.co *******************************************/ #include<graphics.h> #include<stdio.h> #include<conio.h> void main(void) { int gdriver = DETECT, gmode; int x1 = 200, y1 = 200; int x2 = 300, y2 = 300; clrscr(); initgraph(&gdriver, &gmode, "c:\\turboc3\\bgi"); line(x1, y1, x2, y2); closegraph(); getch(); } / Explanation of Code : 1. int x1=200, y1=200; int x2=300, y2=300; We have declared above variables so that we can keep track of starting and ending point. 2. line(x1,y1,x2,y2); We need to pass just 4 parameters to the line() function. 3. Line Function Draws Line From (x1,y1) to (x2,y2) . Syntax : line(x1,y1,x2,y2); ->Parameter Explanation x1 X Co-ordinate of First Point y1 Y Co-ordinate of First Point x2 X Co-ordinate of Second Point y2 Y Co-ordinate of Second Point / 2. Make Static Countdown*
/******************************************** Statement - Static Countdown Programmer - Vineet Choudhary Written For - http://developerinsider.co ******************************************/ #include <graphics.h> #include <dos.h> #include <conio.h> int main() { int gd = DETECT, gm, i; char a[5]; initgraph( &gd, &gm, "C:\\TURBOC3\\BGI"); settextjustify( CENTER_TEXT, CENTER_TEXT ); settextstyle(DEFAULT_FONT,HORIZ_DIR,50); setcolor(RED); for (i = 30; i >=0; i--) { sprintf(a,"%d",i); outtextxy(getmaxx()/2, getmaxy()/2, a); delay(1000); if ( i == 0 ) break; cleardevice(); } cleardevice(); settextstyle(SANS_SERIF_FONT,HORIZ_DIR,2); outtextxy(300,300,"Project by http://www.turboc.codeplex.com"); delay(5000); closegraph(); return 0; } 3. Draw Moving a Car**
/******************************************** Statement - Move a Car Programmer - Vineet Choudhary Written For - http://developerinsider.co ******************************************/ #include <graphics.h> #include <dos.h> #include <conio.h> main() { int i, j = 0, gd = DETECT, gm; initgraph(&gd,&gm,"C:\\TURBOC3\\BGI"); settextstyle(DEFAULT_FONT,HORIZ_DIR,2); outtextxy(25,240,"Press any key to view the moving car"); getch(); setviewport(0,0,639,440,1); for( i = 0 ; i <= 420 ; i = i + 10, j++ ) { rectangle(50+i,275,150+i,400); rectangle(150+i,350,200+i,400); circle(75+i,410,10); circle(175+i,410,10); setcolor(j); delay(100); if( i == 420 ) break; clearviewport(); } getch(); cleardevice(); settextstyle(SANS_SERIF_FONT,HORIZ_DIR,2); outtextxy(100,200,"Project by http://www.turboc.codeplex.com"); delay(5000); closegraph(); return 0; } 4. Press Me Button Game**
/******************************************** Statement - Press Me Button Game Programmer - Vineet Choudhary Written For - http://developerinsider.co *******************************************/ #include <stdio.h> #include <conio.h> #include <dos.h> #include <graphics.h> #include <stdlib.h> union REGS i, o; int left = 265, top = 250; void initialize_graphics_mode() { int gd = DETECT, gm, error; initgraph(&gd,&gm,"C:\\TURBOC3\\BGI"); error = graphresult(); if (error != grOk) { perror("Error "); printf("Press any key to exit...\n"); getch(); exit(EXIT_FAILURE); } } void showmouseptr() { i.x.ax = 1; int86(0x33,&i,&o); } void hidemouseptr() { i.x.ax = 2; int86(0x33,&i,&o); } void getmousepos(int x,int y) { i.x.ax = 3; int86(0x33,&i,&o); x = o.x.cx; y = o.x.dx; } void draw_bar() { hidemouseptr(); setfillstyle(SOLID_FILL,CYAN); bar(190,180,450,350); showmouseptr(); } void draw_button(int x, int y) { hidemouseptr(); setfillstyle(SOLID_FILL,MAGENTA); bar(x,y,x+100,y+30); moveto(x+5,y); setcolor(YELLOW); outtext("Press me"); showmouseptr(); } void draw() { settextstyle(SANS_SERIF_FONT,HORIZ_DIR,2); outtextxy(100,451,"Project by http://www.turboc.codeplex.com"); setcolor(BLUE); rectangle(0,0,639,450); setcolor(RED); outtextxy(160,25,"Try to press the \"Press me\" button"); outtextxy(210,50,"Press escape key to exit"); setfillstyle(XHATCH_FILL,GREEN); setcolor(BLUE); bar(1,1,75,449); bar(565,1,638,449); showmouseptr(); draw_bar(); draw_button(left,top); } void initialize() { initialize_graphics_mode(); if( !initmouse() ) { closegraph(); printf("Unable to initialize the mouse"); printf("Press any key to exit...\n"); getch(); exit(EXIT_SUCCESS); } draw(); } int initmouse() { i.x.ax = 0; int86(0x33,&i,&o); return ( o.x.ax ); } void get_input() { int x, y; while(1) { getmousepos(&x,&y); / mouse pointer in left of button / if( x >= (left-3) && y >= (top-3) && y <= (top+30+3) && x < left ) { draw_bar(); left = left + 4; if (left > 350) left = 190; draw_button(left,top); } / mouse pointer in right of button / else if (x<=(left+100+3)&&y>=(top-3)&&y<=(top+30+3)&&x>(left+100)) { draw_bar(); left = left - 4; if (left < 190) left = 350; draw_button(left,top); } / mouse pointer above button / else if(x>(left-3) && y>=(top-3) && y<(top) && x<= (left+100+3)) { draw_bar(); top = top + 4; if (top > 320) top = 180; draw_button(left,top); } / mouse pointer below button / else if (x>(left-3)&&y>(top+30)&&y<=(top+30+3)&&x<=(left+100+3)) { draw_bar(); top = top - 4; if (top < 180) top = 320; draw_button(left,top); } if (kbhit()) { if (getkey() == 1) exit(EXIT_SUCCESS); } } } int getkey() { i.h.ah = 0; int86(22,&i,&o); return( o.h.ah ); } main() { initialize(); get_input(); return 0; } 5. Draw Smiling Face Animation*
/******************************************** Statement - Smiling Face Animation Programmer - Vineet Choudhary Written For - http://developerinsider.co *******************************************/ #include<graphics.h> #include<conio.h> #include<stdlib.h> main() { int gd = DETECT, gm, area, temp1, temp2, left = 25, top = 75; void p; initgraph(&gd,&gm,"C:\\TURBOC3\\BGI"); setcolor(YELLOW); circle(50,100,25); setfillstyle(SOLID_FILL,YELLOW); floodfill(50,100,YELLOW); setcolor(BLACK); setfillstyle(SOLID_FILL,BLACK); fillellipse(44,85,2,6); fillellipse(56,85,2,6); ellipse(50,100,205,335,20,9); ellipse(50,100,205,335,20,10); ellipse(50,100,205,335,20,11); area = imagesize(left, top, left + 50, top + 50); p = malloc(area); setcolor(WHITE); settextstyle(SANS_SERIF_FONT,HORIZ_DIR,2); outtextxy(20,451,"Smiling Face Project by http://www.turboc.codeplex.com"); setcolor(BLUE); rectangle(0,0,639,449); while(!kbhit()) { temp1 = 1 + random ( 588 ); temp2 = 1 + random ( 380 ); getimage(left, top, left + 50, top + 50, p); putimage(left, top, p, XOR_PUT); putimage(temp1 , temp2, p, XOR_PUT); delay(500); left = temp1; top = temp2; } getch(); closegraph(); return 0; } 6. Make Traffic Light Simulation

1. Drawing Line in Graphics Mode

/**********************************************
 Statement - Drawing Line in Graphics Mode
 Programmer - Vineet Choudhary
 Written For - http://developerinsider.co
 **********************************************/

#include<graphics.h>
#include<stdio.h>
#include<conio.h>

void main(void) {
    int gdriver = DETECT, gmode;
    int x1 = 200, y1 = 200;
    int x2 = 300, y2 = 300;
    clrscr();
    
    initgraph(&gdriver, &gmode, "c:\\turboc3\\bgi");
    line(x1, y1, x2, y2);
    closegraph();
    getch();
}

/*
 
Explanation of Code :
1. int x1=200, y1=200;
   int x2=300, y2=300;
   We have declared above variables so that we can keep track of starting and ending point.
 
2. line(x1,y1,x2,y2);
   We need to pass just 4 parameters to the line() function.
 
3. Line Function Draws Line From (x1,y1) to (x2,y2) .
    Syntax : line(x1,y1,x2,y2);
    ->Parameter	Explanation
        x1	X Co-ordinate of First Point
        y1	Y Co-ordinate of First Point
        x2	X Co-ordinate of Second Point
        y2	Y Co-ordinate of Second Point
*/

2. Make Static Countdown

/**********************************************
 Statement - Static Countdown
 Programmer - Vineet Choudhary
 Written For - http://developerinsider.co
 **********************************************/
#include <graphics.h>
#include <dos.h>
#include <conio.h>
 
int main()
{
   int gd = DETECT, gm, i;
   char a[5];

   initgraph( &gd, &gm, "C:\\TURBOC3\\BGI");

   settextjustify( CENTER_TEXT, CENTER_TEXT );
   settextstyle(DEFAULT_FONT,HORIZ_DIR,50);
   setcolor(RED);
   for (i = 30; i >=0; i--)
   {
      sprintf(a,"%d",i);
      outtextxy(getmaxx()/2, getmaxy()/2, a);
      delay(1000);

      if ( i == 0 )
	 break;
      cleardevice();
   }
   cleardevice();
   settextstyle(SANS_SERIF_FONT,HORIZ_DIR,2);
   outtextxy(300,300,"Project by http://www.turboc.codeplex.com");
   delay(5000);
   closegraph();
   return 0;
}

3. Draw Moving a Car

/**********************************************
 Statement - Move a Car
 Programmer - Vineet Choudhary
 Written For - http://developerinsider.co
 **********************************************/
#include <graphics.h>
#include <dos.h>
#include <conio.h> 
 
main()
{
   int i, j = 0, gd = DETECT, gm;
 
   initgraph(&gd,&gm,"C:\\TURBOC3\\BGI");
 
   settextstyle(DEFAULT_FONT,HORIZ_DIR,2);
   outtextxy(25,240,"Press any key to view the moving car");
 
   getch();
   setviewport(0,0,639,440,1);
 
   for( i = 0 ; i <= 420 ; i = i + 10, j++ )
   {
      rectangle(50+i,275,150+i,400);
      rectangle(150+i,350,200+i,400);
      circle(75+i,410,10);
      circle(175+i,410,10);
      setcolor(j);
      delay(100);
 
      if( i == 420 )
         break;
 
      clearviewport();
   }
   getch();
   cleardevice();
   settextstyle(SANS_SERIF_FONT,HORIZ_DIR,2);
   outtextxy(100,200,"Project by http://www.turboc.codeplex.com");
   delay(5000);
   closegraph();
   return 0;
}

4. Press Me Button Game

/**********************************************
 Statement - Press Me Button Game	
 Programmer - Vineet Choudhary
 Written For - http://developerinsider.co
 **********************************************/
 
#include <stdio.h>
#include <conio.h>
#include <dos.h>
#include <graphics.h>
#include <stdlib.h>
 
union REGS i, o;
int left = 265, top = 250;
 
void initialize_graphics_mode()
{
  int gd = DETECT, gm, error;
 
  initgraph(&gd,&gm,"C:\\TURBOC3\\BGI");
 
  error = graphresult();
 
  if (error != grOk)
  {
    perror("Error ");
    printf("Press any key to exit...\n");
    getch();
    exit(EXIT_FAILURE);
  }
}
 
void showmouseptr()
{
  i.x.ax = 1;
  int86(0x33,&i,&o);
}
 
void hidemouseptr()
{
  i.x.ax = 2;
  int86(0x33,&i,&o);
}
 
void getmousepos(int *x,int *y)
{
  i.x.ax = 3;
  int86(0x33,&i,&o);
 
  *x = o.x.cx;
  *y = o.x.dx;
}
 
void draw_bar()
{
  hidemouseptr();
  setfillstyle(SOLID_FILL,CYAN);
  bar(190,180,450,350);
  showmouseptr();
}
 
void draw_button(int x, int y)
{
  hidemouseptr();
  setfillstyle(SOLID_FILL,MAGENTA);
  bar(x,y,x+100,y+30);
  moveto(x+5,y);
  setcolor(YELLOW);
  outtext("Press me");
  showmouseptr();
}
 
void draw()
{
  settextstyle(SANS_SERIF_FONT,HORIZ_DIR,2);
  outtextxy(100,451,"Project by http://www.turboc.codeplex.com");
  setcolor(BLUE);
  rectangle(0,0,639,450);
  setcolor(RED);
  outtextxy(160,25,"Try to press the \"Press me\" button");
  outtextxy(210,50,"Press escape key to exit");
  setfillstyle(XHATCH_FILL,GREEN);
  setcolor(BLUE);
  bar(1,1,75,449);
  bar(565,1,638,449);
  showmouseptr();
  draw_bar();
  draw_button(left,top);
}
 
void initialize()
{
  initialize_graphics_mode();
 
  if( !initmouse() )
  {
    closegraph();
    printf("Unable to initialize the mouse");
    printf("Press any key to exit...\n");
    getch();
    exit(EXIT_SUCCESS);
  }
 
  draw();
}
 
int initmouse()
{
  i.x.ax = 0;
  int86(0x33,&i,&o);
  return ( o.x.ax );
}
 
void get_input()
{
  int x, y;
 
  while(1)
  {
    getmousepos(&x,&y);
 
    /* mouse pointer in left of button */
 
    if( x >= (left-3) && y >= (top-3) && y <= (top+30+3) && x < left )
    {
      draw_bar();
      left = left + 4;
 
      if (left > 350)
        left = 190;
 
      draw_button(left,top);
    }
 
    /* mouse pointer in right of button */
 
    else if (x<=(left+100+3)&&y>=(top-3)&&y<=(top+30+3)&&x>(left+100))
    {
      draw_bar();
      left = left - 4;
 
      if (left < 190)
        left = 350;
 
      draw_button(left,top);
    }
 
    /* mouse pointer above button */
 
    else if(x>(left-3) && y>=(top-3) && y<(top) && x<= (left+100+3))
    {
      draw_bar();
      top = top + 4;
 
      if (top > 320)
        top = 180;
 
      draw_button(left,top);
    }
 
    /* mouse pointer below button */
 
    else if (x>(left-3)&&y>(top+30)&&y<=(top+30+3)&&x<=(left+100+3))
    {
      draw_bar();
      top = top - 4;
 
      if (top < 180)
        top = 320;
 
      draw_button(left,top);
    }
 
    if (kbhit())
    {
      if (getkey() == 1)
        exit(EXIT_SUCCESS);
    }
  }
}
 
int getkey()
{
  i.h.ah = 0;
  int86(22,&i,&o);
 
  return( o.h.ah );
}
 
main()
{
  initialize();
 
  get_input();
  return 0;
}

5. Draw Smiling Face Animation

/**********************************************
 Statement - Smiling Face Animation	
 Programmer - Vineet Choudhary
 Written For - http://developerinsider.co
 **********************************************/
 
#include<graphics.h>
#include<conio.h>
#include<stdlib.h>
 
main()
{
   int gd = DETECT, gm, area, temp1, temp2, left = 25, top = 75;
   void *p;
 
   initgraph(&gd,&gm,"C:\\TURBOC3\\BGI");
 
   setcolor(YELLOW);
   circle(50,100,25);
   setfillstyle(SOLID_FILL,YELLOW);
   floodfill(50,100,YELLOW);
 
   setcolor(BLACK);
   setfillstyle(SOLID_FILL,BLACK);
   fillellipse(44,85,2,6);
   fillellipse(56,85,2,6);
 
   ellipse(50,100,205,335,20,9);
   ellipse(50,100,205,335,20,10);
   ellipse(50,100,205,335,20,11);
 
   area = imagesize(left, top, left + 50, top + 50);
   p = malloc(area);
 
   setcolor(WHITE);
   settextstyle(SANS_SERIF_FONT,HORIZ_DIR,2);
   outtextxy(20,451,"Smiling Face Project by http://www.turboc.codeplex.com");
 
   setcolor(BLUE);
   rectangle(0,0,639,449);
 
   while(!kbhit())
   {
      temp1 = 1 + random ( 588 );
      temp2 = 1 + random ( 380 );
 
      getimage(left, top, left + 50, top + 50, p);
      putimage(left, top, p, XOR_PUT);
      putimage(temp1 , temp2, p, XOR_PUT);
      delay(500);
      left = temp1;
      top = temp2;
   }
 
   getch();
   closegraph();
   return 0;
}

6. Make Traffic Light Simulation

Introduction - C Programming

1. What is C?

2. Feature of C Program

3. C program structure

4. C Keywords

5. C Character Set

6. Rules for Writing, Compiling and Executing the C program

7. Data types & Placeholders

8. Control characters (Escape sequences)

9. Receiving input values from keyboard

Expression & Operators Precedence - C Programming

The Decision Control Structure - C Programming

1. The if Statement

2. The if-else Statement

3. Nested if-elses

4. The if-else Ladder/else-if Clause

5. Switch Statements or Control Statements

6. switch Versus if-else Ladder

The Loop Control Structure - C Programming

1. while loop

Example

2. for loop

Example

3. do-while loop

Example

4. Break and Continue statement

Example 1 (break)

Example 2 (continue)

5. Goto and labels

Example

Array - C Programming

1. Array Declaration

2. Accessing Elements of an Array

3. Entering Data into an Array

4. Reading Data from an Array

5. Advantages of using an Array

6. Disadvantages of using an Array

7. Multidimensional arrays

8. Example

8.1 Simple Array

8.2 Two-Dimensional Array

1. What is String?

2. Point to Note

3. Standard Library String Functions

4. Example

5. Examples

Functions - C Programming

1. What is a Function?

2. Why Use Functions

3. Function arguments

4. Function return values

5. void return value

6. Recursive Function

7. Multiple Parameters

8. Call by value

9. Call by reference

Pointers - C Programming

1. What is a Pointer?

2. C Pointer Syntax

3. Pointer Notation

4. Example

5. Examples

Structures - C Programming

1. Declaring a Structure

2. Accessing Structure Elements

3. Example

4. Structures as Function Arguments

5. Summary

6. Examples

Files Handling - C Programming

1. File Pointers

2. Opening a File

3. Examples

Command Line Arguments - C Programming

For example

Results of Parsing Command Lines

Type Casting - C Programming

1. Implicit Type Conversion

2. Explicit Type Conversion

Example

`#include <file>`

`#include "file"`

`#include anything else`