The standard library’s strlen() counts characters in a string by walking from the first character until it reaches the null terminator (‘\0’) — the zero byte that marks the end of every C string. Implementing strlen() yourself is a classic exercise that teaches exactly how strings work in C. The original post had two serious …
This program converts a given number of days into years, weeks, and remaining days using integer division and modulo arithmetic. The formula uses 365 days per year and 7 days per week (leap years are ignored). It is a straightforward exercise in chained division and remainder operations. The original post used void main() and broken …
A cube is a three-dimensional shape with six equal square faces. Given the side length s, the surface area is 6s² (six faces, each with area s²) and the volume is s³. This program reads the side length and computes both values using only basic arithmetic — no need for pow() and the -lm flag …
Checking whether one string contains another is one of the most common string operations in C. The standard library provides strstr() in <string.h> — it returns a pointer to the first occurrence of the substring in the main string, or NULL if not found. The position of the match is calculated by subtracting the start …
This C program shows how to mask password input with asterisks (*) — exactly what you see on a login screen, where each character you type is hidden behind a *. The trick is to read the keyboard without echoing the typed character to the screen, print a * in its place, and store the …
Inserting an element into an array means placing a new value at a specific position while shifting existing elements to make room. Because C arrays are fixed in size, you need to allocate enough space upfront and track the current number of elements separately. This guide shows two practical approaches: inserting at a given index …