The extern keyword in C declares that a variable or function exists — but is defined somewhere else. It tells the compiler “trust me, this symbol is defined in another translation unit; the linker will resolve it.” Understanding extern is essential for any multi-file C program, and confusing declaration with definition is one of the …
The sizeof operator in C returns the size in bytes of a type or expression. It is evaluated at compile time and is the standard, portable way to determine how much memory any type occupies on the current platform. Because type sizes vary between 32-bit and 64-bit systems and between compilers, you should always use …
Converting strings to numbers is a fundamental task in C — every value read from scanf, fgets, or command-line arguments arrives as a string and must be explicitly converted. The standard library in <stdlib.h> provides three simple conversion functions: atoi() (string to int), atol() (string to long), and atof() (string to double/float). For robust error …
Command line arguments let users pass data to a C program at the moment they run it — without embedding values in the source code or prompting for input. When you run ./copy src.txt dst.txt, the strings src.txt and dst.txt arrive in your program through two special parameters: argc and argv. Understanding them is essential …
Pascal’s Triangle is a triangular array where each number is the sum of the two numbers directly above it. Row n, column k holds the binomial coefficient C(n,k) — the number of ways to choose k items from n. It appears in combinatorics, probability, the binomial theorem, and polynomial expansion. The C program below builds …
Floyd’s triangle in C is a right-angled triangular arrangement of consecutive natural numbers. Row 1 contains 1 number, row 2 contains 2, row 3 contains 3, and so on. It is named after Robert W. Floyd, who used it to teach loop control and nested iteration. The total numbers through row n is 1 + …