C standard function library is a collection of all standard header files, as well as common function library implementation programs, such as I/O input and output and string control. Different from COBOL, Fortran and PL/I, the task of C language does not contain embedded keywords, so almost all C language programs are created by functions of standard function library.
Introduction to c language
C language is a process-oriented computer programming language, which is different from object-oriented programming languages such as C++, C# and Java. The design goal of C language is to provide a programming language that can compile and process low-level memory in a simple way, only generate a small amount of machine code, and does not need any running environment support at runtime.
C language is faster than assembly language in describing problems, less workload, good readability, easy debugging, modification and transplantation, and the code quality is equivalent to that of assembly language. Generally speaking, C language is only less efficient than the target program generated by assembly language code 10%-20%. So C language can write system software.