Convert a string to an integer atoi

2. The string is converted into a long integer atol.

3. The string is converted into a floating-point number strtod.

4. The string is converted into a long integer strtol.

5. The string is converted into an unsigned long integer string.

C language is a general computer programming language, which is widely used. The design goal of C language is to provide a programming language that can compile and process low-level memory in a simple way, generate a small amount of machine code and run without any support of running environment.

Although C language provides many low-level processing functions, it still maintains good cross-platform characteristics. C language programs written in standard specifications can be compiled on many computer platforms, even including some embedded processors (single chip microcomputer or MCU) and supercomputers.