An IPv4 address is displayed as four decimal octets separated by dots (e.g., 192.168.1.1) but is stored internally as a single 32-bit unsigned integer. Converting between the dotted-decimal string and the integer form is a fundamental networking operation — inet_addr() in the POSIX socket API does exactly this. Understanding how to do it manually shows …
This C program compares two strings and reports whether they are equal, or which one comes first in dictionary (lexicographic) order. Comparison works character by character: walk both strings together until two characters differ or a string ends, then decide from that first difference. This page shows a manual character-by-character implementation and the standard library …
The time.h library in C provides functions for getting the current date and time, formatting it for display, and converting between representations. The central type is time_t — typically a 32-bit or 64-bit integer counting seconds since the Unix epoch (1970-01-01 00:00:00 UTC). Five key functions cover the most common time operations: time(), ctime(), localtime(), …
The goto statement in C is an unconditional jump that transfers program control directly to a labelled statement within the same function. While modern C style discourages it, goto is still useful in a few real situations — most commonly for breaking out of deeply nested loops and for centralised cleanup/error handling. In this tutorial …
Variable scope controls where in a program a variable can be accessed. In C, a variable’s scope is determined by where it is declared: variables declared outside all functions have file scope (global), while variables declared inside a function or block have block scope (local). A third kind — static local variables — persist between …
The do-while loop in C is a post-test loop: it executes the body first and checks the condition afterward. This guarantees the body runs at least once, regardless of the condition’s initial truth value. This is the key difference from the while loop, which checks the condition before the first iteration and may never execute …