#stdlib
int    abs(int)
int    system(const char *) (-1 error)

#math
double sqrt(double)
double pow(double x, double n)
double floor(double)
double ceil(double)

#string
int    strcmp(const char *, const char *)
char   *strcpy(char *, const char *) (s1)
strcat
atoi
atof
fopen, fclose, frscanf, fprint, fgetc
print, scanf, gets, getch
rand

Unix commands:
the bash programming statements
setting and getting data from the shell memory
cp, mkdir, rmdir, mv, cat, more, vi, tar, man, chmod
the pipe operators

JV