Three ways to create symbolic constants in C language; printf () and scanf () functions

1, #indefine the macro definition of pi 3.1415926 form

2, const int months=12; This causes MONTHS to become a read-only value.

3. Enum Enum type

4. The printf () and scanf () functions enable us to communicate with the program, they are called input/output functions, (I/O functions)

5, string, floating-point output type and Description: Instance program:

 #include <stdio.h> #define  BLURB  "authentic imitation!" Macro definition Mode Int main (void) { const double rent=3852.99;//Const method-defined constants/* Following are the use of some format flags */printf ("%x  %x  % #X \ n ", 31,31,31); the hexadecimal representation of//%X31 indicates that the hexadecimal representation of 31 is 1F; use # to make the output start with 0x 0x1f;printf (" **%d**%d**%d**\ n ", 42,42,-42);p rintf (" **%5d**%5.3d**%05.3d**\n ", 6,6,6,6);/* The case in the string is as follows: */printf ("/%2s/\n ", BLURB);//Default output printf ("/ %24s/\n ", BLURB);//create 24bit space in memory, the characters are not enough to fill with blanks from the left. printf ("/%24.5s/\n", BLURB), or//a total of 24 space, but the precision required to retain 5 bits, preceded by a space. printf ("/%-24.5s/\n", BLURB);//Ibid., just-indicates that left alignment is required. /* Following is a combination of some floating-point numbers */printf ("*%f*\n", RENT);p rintf ("*%e*\n", RENT);p rintf ("*%4.2f*\n", RENT);p rintf ("*%3.1f*\n", RENT); /By the output is not difficult to see, 3.1f represents the output should be a total of three bits, 1 for precision, so there is rounding, the original number of more than 3, automatic expansion. printf ("*%10.3f*\n", RENT);//output should be a total of 10, not enough words from the left to start the space, after the decimal point there are 3 digits, the number of decimals is not enough to use 0-fill printf ("*%10.3e*\n", RENT);p rintf ("*%+4.2f* \ n ", RENT);p rintf (" *%010.2f*\n ", RENT);//represents 10 bits in 0 and 2 for precision. return 0;} 

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Three ways to create symbolic constants in C language; printf () and scanf () functions