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A low-level systems programming language. The foundation for operating systems, embedded systems, and performance-critical code.
Dennis Ritchie created C at Bell Labs between 1969 and 1973 to rewrite the Unix operating system, and it has remained foundational to computing ever since. Nearly every operating system kernel — Linux, Windows, macOS, and the BSDs — is written primarily in C. The language provides direct access to memory through pointers, manual memory management via malloc/free, and minimal runtime overhead, making it the standard choice for embedded systems, device drivers, real-time systems, and performance-critical libraries.
C's influence is immeasurable: its syntax shaped C++, Java, C#, JavaScript, and dozens of other languages. The standard library is deliberately small, covering string manipulation, I/O, and basic math, leaving everything else to platform APIs and third-party libraries. Compilers like GCC, Clang, and MSVC produce highly optimized machine code across virtually every processor architecture, from 8-bit microcontrollers to supercomputers.
The language is standardized by ISO, with major revisions including C99 (variable-length arrays, inline functions), C11 (threads, atomics), and C23 (type-generic expressions, nullptr). Despite lacking modern safety features like bounds checking and automatic memory management, C remains irreplaceable where hardware control, deterministic performance, and minimal footprint are non-negotiable. Database engines (SQLite, PostgreSQL), language runtimes (CPython, Ruby MRI), cryptographic libraries (OpenSSL), and networking stacks all rely on C as their foundation.
C's lack of memory safety means that every pointer arithmetic change, buffer size modification, and free/malloc pairing must be scrutinized. Comparing C files catches off-by-one errors in array access, modified NULL checks that introduce segfaults, changed struct layouts that break binary compatibility, and altered preprocessor macros that affect conditional compilation across platforms.
Security auditors diff C patches to verify that vulnerability fixes — buffer overflows, use-after-free, format string bugs — are complete and correct.
UtraDiff compares C source files with C syntax highlighting, covering preprocessor directives, pointer declarations, and struct definitions. Side-by-side view aligns function signatures and macro blocks across panels for line-by-line review. The whitespace ignore toggle suppresses brace-style reformatting noise.
Alt+Arrow navigation jumps between changed sections, critical for reviewing security patches. Language-aware tokenization distinguishes type changes from variable modifications in pointer arithmetic expressions.
Supported extensions: .c .h