C

C came out of Bell Labs in 1972, written to build the Unix operating system, and most of computing still rests on it: Python, R, PostgreSQL, and the core of NumPy are all written largely in C. Here it is compiled with GCC using the C17 standard, with every warning turned into an error.

Its standard library is small. It has sqrt, log, and exp, qsort for sorting, and printf for output, but no growable arrays, no hash tables, no CSV reader, and no string type beyond an array of characters. So the implementations do their own bookkeeping: they grow arrays with realloc, split lines with strtok, and release memory with free, because nothing does it for you.

Quirks

• The math functions live in a separate library. Without -lm on the compile line, a call to log fails with “undefined reference to log”.
• An array passed to a function arrives as a bare pointer, so it forgets its length. sizeof on a three-int array gives 12 bytes where it’s declared, and 8, the size of a pointer, inside the function.
• 7 / 2 is integer division, giving 3, and -7 / 2 gives −3: C rounds toward zero.
• Unsigned numbers wrap around: an unsigned int holding 0, minus 1, is 4294967295. Sizes and counts (size_t) are unsigned, so a loop that counts down to 0 needs care.

git clone https://github.com/qnixon/dswithx.git
cd dswithx
python3 harness/run_tests.py --language c