C Master

Ace Your C Exam

A complete, mobile-friendly reviewer for college students covering Functions, Arrays, Strings, and Pointers.

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01

Functions

Modular Programming

What & Why?

A function is a block of code that performs a specific task. Every C program has at least one function: main().

Declaration The "Prototype". Tells compiler function exists.
Definition The "Body". The actual code logic.
Call Executing the function.
basic_function.c 
#include <stdio.h>

// 1. Declaration (Prototype)
int add(int a, int b); 

int main() {
    int sum = add(5, 10); // 3. Call
    printf("Sum: %d", sum);
    return 0;
}

// 2. Definition
int add(int a, int b) {
    return a + b;
}

Recursion

A function calling itself. Must have a Base Case to stop infinite recursion.

factorial.c 
int factorial(int n) {
    if (n == 0) 
        return 1; // Base Case
    else 
        return n * factorial(n - 1); // Recursive Call
}
02

Arrays

Data Structures

A collection of variables of the same type. Index starts at 0.

int arr[5] = {10, 20, 30, 40, 50};
idx 0
10
idx 1
20
idx 2
30
idx 3
40
idx 4
50

2D Arrays (Matrices)

Syntax: type name[rows][cols];

int matrix[2][3] = {
    {1, 2, 3},  // Row 0
    {4, 5, 6}   // Row 1
};
// Accessing number 6:
int val = matrix[1][2];  // Row 1, Column 2

Critical Rule

When you pass an array to a function, you are passing the memory address. Changes inside the function affect the original array.

03

Strings

Character Arrays

A string is a char array ending with a Null Terminator \0.

char str[] = "Hello";
'H'
'e'
'l'
'l'
'o'
\0

String Library Functions (<string.h>)

Function Purpose Example
strlen(s) Length (excluding \0) strlen("Hi") → 2
strcpy(dst, src) Copy src to dst strcpy(d, "Text")
strcmp(s1, s2) Compare (0 if equal) strcmp("a","a") → 0
strcat(dest, src) Append src to dest strcat(s1, " more")
04

Pointers

Memory Management

A pointer stores the memory address of another variable.

&
Address-of
"Where does it live?"
*
Dereference
"What is inside that address?"

Basic Pointer Usage

int x = 10;
int *ptr = &x;     // ptr holds address of x

printf("Value: %d\n", *ptr);      // Prints: 10
printf("Address: %p\n", ptr);     // Prints memory address

*ptr = 20;                // x is now 20
05

Quiz

Test Your Knowledge

Quiz Progress 0/0 answered

Practical: Super Calculator

Combines Functions, Switch Cases, and Parameters.

#include <stdio.h>

// Function prototypes
float add(float a, float b) { return a + b; }
float subtract(float a, float b) { return a - b; }
float multiply(float a, float b) { return a * b; }
float divide(float a, float b) {
    if (b == 0) {
        printf("Error! Division by zero.\n");
        return 0;
    }
    return a / b;
}

int main() {
    float n1, n2;
    char op;
    
    printf("Enter (e.g. 10 + 5): ");
    scanf("%f %c %f", &n1, &op, &n2);
    
    switch(op) {
        case '+':
            printf("Result: %.2f", add(n1, n2));
            break;
        case '*':
            printf("Result: %.2f", multiply(n1, n2));
            break;
        default:
            printf("Invalid operator");
    }
    return 0;
}

Quick Cheat Sheet

Topic Syntax Note
Function int func(int x); Declare before main
Array int a[5]; Index 0 to 4
String char s[10]; Needs \0 terminator
Pointer int *p = &x; *p gets value, p gets addr
2D Array int m[3][4]; matrix[row][col]
Recursion return n * f(n-1); Needs base case

Practice Tips

  • Compile with warnings: gcc -Wall -Wextra file.c
  • Use online compilers: onlinegdb.com, replit.com
  • Write small test programs for each concept
  • Trace code with pen and paper (pointers & recursion)