Topic 2- Strings

Tags: #◇CCPROG2 #◇C Programming #◇Programming #◇Computer Science #◇Data Types #◇Data Structures #◇Structured Data #◇Structured Programming #◇Memory Management

◇Overview

In C, strings are null-terminated arrays of characters. There is no dedicated string type — strings are represented as char arrays ending with '\0'.

◇Key Concepts

A string is a char array terminated by '\0' String literals (e.g., "Hello") are stored in read-only memory The <string.h> library provides essential string functions scanf("%s", ...) stops at whitespace; fgets() reads full lines

◇Details / Theory

String Declaration and Initialization

char str1[6] = "Hello";                // Size 6: 'H','e','l','l','o','\0'
char str2[] = "Hello";                  // Compiler infers size = 6
char str3[6] = {'H','e','l','l','o','\0'};  // Character-by-character
char *str4 = "Hello";                   // Pointer to string literal (read-only)

String Input/Output

char name[50];

// scanf — stops at whitespace
scanf("%s", name);

// fgets — reads entire line (safer, includes newline)
fgets(name, sizeof(name), stdin);

// printf
printf("Name: %s\n", name);

// puts — prints string + newline
puts(name);

Common <string.h> Functions

String Comparison

char a[] = "apple";
char b[] = "banana";

if (strcmp(a, b) < 0)
    printf("%s comes before %s\n", a, b);
// Cannot use == to compare strings; that compares addresses

String Manipulation Example

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

int main() {
    char first[20] = "John";
    char last[20] = "Doe";
    char full[50];

    strcpy(full, first);   // full = "John"
    strcat(full, " ");     // full = "John "
    strcat(full, last);    // full = "John Doe"

    printf("Full name: %s (length: %lu)\n", full, strlen(full));
    return 0;
}

Character Functions (<ctype.h>)

◇Common Pitfalls

Using == to compare strings instead of strcmp(). Buffer overflow: writing more characters than array size allows. Forgetting the null terminator when building strings manually. scanf("%s", ...) is unsafe — no bounds checking. Prefer fgets(). Modifying a string literal via pointer (char *s = "abc"; s[0] = 'x'; → undefined behavior).

◇Summary

TL;DR — C strings are null-terminated char arrays. Use <string.h> functions (strlen, strcpy, strcmp, strcat) for manipulation. Always ensure buffers are large enough and terminated with '\0'. Never compare strings with ==.

◇Links

Related: ◇What is an Array — ◇Declaration — ◇Accessing Elements — ◇Structs — ◇File Handling Source / Reference:

◇References & Navigation

• Previous Topic: ◇Advantages and Disadvantages
• Next Topic: ◇Structs
• Related Notes: ◇One-Dimensional Arrays (1D Arrays), ◇Data Representation - Characters and Boolean