Table of Contents

1. History of C
2. Basics & Syntax
3. Pointers & Memory
4. Advanced Topics
5. Practical — compile, run, debug
6. Common pitfalls & best practices
7. Exercises & Solutions
8. Cheat-sheet (quick ref)

History of C

C was developed by Dennis Ritchie at AT&T Bell Labs in the early 1970s as a system programming language to implement the Unix operating system. It evolved from earlier languages like B and BCPL. C gained popularity due to its mix of performance, expressiveness, and memory control. It has influenced many later languages (C++, C#, Java) and is still widely used in system programming, embedded systems, and performance-critical applications.

1) Basics & Syntax

1.1 Structure of a C program

A typical C program contains: preprocessor directives, the main() function, declarations, statements, and a return value.

#include <stdio.h>

int main(void) {
    printf("Hello, world!\n");
    return 0;
}
            

1.2 Data types & variables

Primary types: int, char, float, double, with modifiers like signed, unsigned, short, long.

int a = 10;
char c = 'A';
float f = 3.14f;
double d = 2.71828;
unsigned int u = 4000000000u;
        

Size & limits

Sizes depend on architecture. Use sizeof() and <limits.h> for exact values.

1.3 Operators

Types: arithmetic (+ - * / %), relational (== != < > <= >=), logical (&& || !), bitwise (& | ^ ~ << >>), assignment (= += -=), ternary (? :).

1.4 Control flow

// if-else
if (x > 0) {
  // do something
} else {
  // else
}

// switch
switch (ch) {
  case 'a':
    break;
  default:
    break;
}

// loops
for (int i = 0; i < n; i++) { }
while (cond) { }
do { } while (cond);
        

1.5 Functions

#include <stdio.h>

int add(int a, int b); // prototype

int main(void) {
    printf("%d\n", add(2,3));
    return 0;
}

int add(int a, int b) {
    return a + b;
}
        

1.6 Arrays & Strings

int arr[5] = {1,2,3,4,5};
char s[] = "Hello";
        

2) Pointers & Memory

int x = 5;
int *p = &x;
*p = 10;
printf("%d\n", x);
        

3) Advanced Topics

3.1 Structs & Unions

struct Person {
    char name[50];
    int age;
};

struct Person p = {"Amina", 25};
printf("%s is %d\n", p.name, p.age);
        

3.2 File I/O

FILE *f = fopen("data.txt", "w");
if (f) {
    fprintf(f, "Hello\n");
    fclose(f);
}
        

3.3 Dynamic memory

int *arr = malloc(5 * sizeof *arr);
if (!arr) { /* handle error */ }
free(arr);
        

4) Practical — Compile, Run, Debug

gcc -Wall -Wextra -std=c17 -O2 main.c -o main
./main
        

5) Common Pitfalls & Best Practices

• Always initialize variables.
• Check return values.
• Validate array indices.
• Use const where possible.

6) Exercises (Theory + Practical) — with Answers

// Example exercise solution
#include <stdio.h>
int main(void){
    char name[100];
    printf("Enter name: ");
    if (fgets(name, sizeof name, stdin)){
        char *p = name;
        while (*p) { if (*p == '\n') { *p = '\0'; break; } p++; }
        printf("Hello, %s\n", name);
    }
    return 0;
}
        

7) Cheat-sheet (Quick Reference)

• Compile: gcc -std=c17 -Wall -Wextra -O2 file.c -o prog
• Debug: gcc -g file.c -o prog then gdb ./prog