Scattered knowledge of C language (unfinished)

Catalog

Units in a computer

Reference header file

main function

Declare variables

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Units in a computer

         bit bits

                1001 0110  Every 2 Hexadecimal bits occupy one bit

         byte byte       1byte = 8bit

                A byte is a unit of data , And it's the smallest unit hardware can access

         kb                 1kb = 1024byte

         mb                1mb = 1024kb

         gb                 1gb = 1024mb

         tb                  1tb = 1024gb

         pb                 tpb = 1024tb

Reference header file

        #include <stdio.h> 

         include Is the meaning of inclusion , Used to reference header files

main function

        main Function is the entry of a program

         In a project main There is and only one function

         （ There can be more than one in a project .c file , But many .c There can only be one... In the file main function ）

Declare variables

        In a project , When in B.c After defining global variables in the file , If you need to A.c Use this global variable in the file , You need to in A.c The global variable is declared in the file . for example ：

extern int quanju1;

int main()
{
    printf("%d\n", quanju1);

    return 0;
} 

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