C Programming Complete Course Manual

1. History of 'C'

'C' is a powerful programming language which has attracted worldwide adoption because software industries rely on it for high-performance computing. A program written in 'C' can be transferred easily from one computer system to another with minimal or no changes. Programs written in 'C' execute fast and efficiently. This versatility makes 'C' a desirable language in the highly competitive software industry.

A system programmer named Dennis Ritchie developed the 'C' language at Bell Laboratories in early 1972. It was written originally for programming under the Unix operating system. The language derives from earlier work by Ken Thompson, who created the 'B' language based on B.C.P.L (Basic Combined Programming Language). Thompson dubbed his version 'B', and later Dennis Ritchie chose the second letter of B.C.P.L—'C'—to represent the improved successor language.

2. Character Set & Identifiers

'C' uses the following set of valid characters:

• Letters: Upper case A – Z, Lower case a – z
• Digits: 0 – 9
• Special Characters: *, (, ), #, &, [, ], ", ', +, -, <, >, =, _, etc.

Identifiers

Identifiers are names given to various program elements such as variables, functions, and arrays. An identifier consists of letters and digits in any order, except that the first character must be a letter or an underscore (_).

3. Keywords (Reserved Words)

Reserved words in 'C' are called keywords. These keywords have predefined meanings to the compiler and cannot be used as user-defined identifiers. All reserve words must be written in lower case letters.

4. Data Types, Sizes & Ranges

'C' provides several basic data types along with qualifiers (short, long, signed, unsigned):

5. Constants & Escape Sequences

'C' has four basic types of constants: Integer constants, Floating point constants, Character constants (enclosed in single quotes `'a'`), and String constants (enclosed in double quotes `"srinivas"`).

Escape Sequences Table

An escape sequence begins with a backslash (\) followed by special control characters:

6. Variables & Declarations

A variable is a named memory location used to represent specified information. Variables must be declared before they are used in executable statements.

// Syntax: data_type variable1, variable2;
int a, b, c;
char ch;
float sum;

// Variable Initialization
int value = 5;
char name[10] = "srinivas";

7. Operators & Expressions

A. Arithmetic Operators

+ (Addition), - (Subtraction), * (Multiplication), / (Division), % (Modulus - remainder after integer division).

B. Relational Operators

< (Less than), > (Greater than), <= (Less than or equal), >= (Greater than or equal), == (Equal to), != (Not equal).

C. Logical & Assignment Operators

Logical: && (AND), || (OR), ! (NOT).
Compound Assignment: +=, -=, *=, /=, %= (e.g. a += 2 is equivalent to a = a + 2).

D. Unary Operators

Operators acting on a single operand: Increment (++), Decrement (--), Size of operator (sizeof).

8. Input/Output (getchar, putchar, printf, scanf)

Conversion Characters for Formatted I/O

Program: Reading & Displaying Character

#include <stdio.h>

int main() {
    char a;
    printf("Enter a character: ");
    a = getchar();
    printf("You entered: ");
    putchar(a);
    return 0;
}

9. Branching (If-Else Statements)

The if-else statement evaluates a condition to select between two decision paths.

#include <stdio.h>

int main() {
    int n;
    printf("Enter a number: ");
    scanf("%d", &n);

    if (n % 2 == 0) {
        printf("The number %d is EVEN\n", n);
    } else {
        printf("The number %d is ODD\n", n);
    }

    return 0;
}

10. Looping (While, Do-While, For)

Program: Check Prime Number (While Loop)

#include <stdio.h>

int main() {
    int n, i = 1, count = 0;
    printf("Enter any positive integer: ");
    scanf("%d", &n);

    while (i <= n) {
        if (n % i == 0) {
            count++;
        }
        i++;
    }

    if (count == 2) {
        printf("%d is a Prime Number\n", n);
    } else {
        printf("%d is Not a Prime Number\n", n);
    }

    return 0;
}

Program: Number Pyramid Pattern (For Loop)

#include <stdio.h>

int main() {
    int n = 4, i, j;
    for (i = 1; i <= n; i++) {
        for (j = 1; j <= i; j++) {
            printf("%d ", j);
        }
        printf("\n");
    }
    return 0;
}
/* Output:
1
1 2
1 2 3
1 2 3 4
*/

11. Arrays & Multi-Dimensional Matrices

An array is a collection of similar data elements stored in contiguous memory locations.

Program: Matrix Addition (2x2)

#include <stdio.h>

int main() {
    int a[2][2] = {{1, 2}, {3, 4}};
    int b[2][2] = {{5, 6}, {7, 8}};
    int sum[2][2], i, j;

    for (i = 0; i < 2; i++) {
        for (j = 0; j < 2; j++) {
            sum[i][j] = a[i][j] + b[i][j];
            printf("%d\t", sum[i][j]);
        }
        printf("\n");
    }
    return 0;
}

12. Strings & String Library Functions

A string in 'C' is a 1D character array terminated by a null character (\0). Standard string functions in <string.h>:

• strcpy(dest, src) - Copies string src into dest.
• strcat(str1, str2) - Appends str2 to the end of str1.
• strcmp(str1, str2) - Compares two strings (returns 0 if identical).
• strrev(str) - Reverses the characters in a string.

13. Goto & Unconditional Statements

#include <stdio.h>

int main() {
    int n = 5, i = 1;
    loop_start:
    printf("%d x %d = %d\n", n, i, n * i);
    i++;
    if (i <= 10) {
        goto loop_start;
    }
    return 0;
}

14. Switch Case Statement

#include <stdio.h>

int main() {
    int a = 10, b = 5, choice = 1;

    switch(choice) {
        case 1: printf("Addition: %d\n", a + b); break;
        case 2: printf("Subtraction: %d\n", a - b); break;
        default: printf("Invalid choice\n"); break;
    }
    return 0;
}

15. Functions & Modular Programming

Functions allow breaking programs into modular, reusable blocks.

#include <stdio.h>

int calculateArea(int length, int width) {
    return length * width;
}

int main() {
    int area = calculateArea(12, 5);
    printf("Area of Rectangle: %d\n", area);
    return 0;
}

16. Storage Classes in C

Storage classes determine the scope, lifetime, and initial value of variables:

• auto: Local variable created on function entry and destroyed on exit.
• extern: Global variable accessible across multiple files.
• static: Retains its current value across multiple function calls.
• register: Requests compiler to store variable in fast CPU registers.

17. Structures & Dynamic Memory

#include <stdio.h>
#include <string.h>

struct Student {
    char name[50];
    int rollNo;
};

int main() {
    struct Student s1;
    strcpy(s1.name, "Ramu K.");
    s1.rollNo = 101;

    printf("Student: %s, Roll: %d\n", s1.name, s1.rollNo);
    return 0;
}