C language string and formatted input and output

1. Preamble procedure

1#include <stdio.h>2#include <string.h>//1 function Prototypes for strlen ()3 #defineDENSITY 62.4//2 preprocessing commands4 intMainvoid)5 {6     floatWeight,volume;7     intsize,letters;8     Charname[ +];//3 Defining an array of length 409 Tenprintf"hi! What ' s your first name?\n"); Onescanf"%s", name); Aprintf"%s,what ' s your weight in pounds?\n", name); -scanf"%f",&weight); -Size=sizeofName//4 Length of array name[] theLetters=strlen (name);//5 calling Function strlen () -volume=weight/DENSITY; -printf"Well,%s,your volume is%2.2f cubic feet.\n", Name,volume);//%2.2f indicates a character width of 2 and is accurate to two digits after the decimal point -printf"Also,your First name has%d letters,\n", letters); +printf"And we have%d bytes to store it in.\n", size); -     return 0; +}

2. About strings

(1) A string is a sequence of one or more characters. such as "I am a student!".

(2) The C language uses null characters to mark the end of a string. The number of cells in the array must be at least 1 more than the number of characters to store.

(3) string and character. The difference between ' x ' and ' X ' (the latter is a string consisting of ' X ' and ' s ').

(4) Sizeof () and strlen () functions.

• • The same string, sizeof () calculates the null character at the end of the flag string, which is 1 larger than strlen ().
  • Strlen () gives the length of the string in characters . sizeof () gives the length of the array (the allocated memory unit).
  • Gets a type large size ~ Gets the size of a specific amount. sizeof (char) and sizeof (name) =sizeof name.

1 sizeof() and strlen ()2#include <stdio.h>3#include <string.h>4 #definePraise "What a Super Marvelous name!"5 intMainvoid)6 {7     Charname[ +];8printf"What ' s your name?\n");9scanf"%s", name);Tenprintf"hello,%s.%s\n", name,praise); Oneprintf"Your name of%d Letrers occupies%d memory cells.\n", Astrlen (name),sizeof(name));//sizeof name -printf"The phrase of praise has%d letters", - strlen (Praise)); theprintf"And occupies%d memory cells.\n",sizeof(praise));//sizeof Praise -     return 0; -}

3. Constants and C-preprocessor

(1) Constants such as 0.015. Float taxrate=0.015. Assign a constant of 0.015 to the variable taxrate, but the program may accidentally change its value.

(2) Two methods of the Const modifier and the # define preprocessing command

• • const int months=12;
  • #define MONTHS +12; (#define TEE ' T ') (#define OOPS "now has it!")

4.printf () function

(1) printf ():("Control description" + variable list) ~ (the variable uses a value, whether the value is a variable, constant, or expression).

(2) printf () conversion specifier:%c--a character,%d--signed decimal integer,%e--floating-point number e notation,%, f--floating-point decimal,%p--pointer,%%--print a%,%s--string ... ：

• • Please avoid mismatched conversions.

(3) printf () marker:-(left-aligned), + (Signed), # (...), 0 (for all number formats, with leading 0 padding field widths)

• • Prints the first 8 characters of a string with a field width of 8 characters (%8.8s)
  • Print double quotation marks \ ".... \"
  • Prints a field width in the parameter list for the given octal integer (%*0).
  • %5D (00006)
  • Specify fixed field width (effectively prevent overflow)

(4) Print a longer string with printf ()

A. Use multiple printf () functions;

B. using (\) and enter in a printf ()

C. Using the string Join method ("Hello" "World")

1 printf () prints longer strings2#include <stdio.h>3 intMainvoid)4 {5printf"Here's one to print a");6printf"Long string.\n");//a7printf"Here's another to print a \8 Long string. \ n");//b9printf"Here's the newest to print a"Ten         "Long string.\n");//C One     return 0; A}

(5) The function return value of printf () returns the number of characters printed, and returns 1 if the output is incorrect, often used to check for output errors. To a file rather than a screen)

1 The return value of printf ()2#include <stdio.h>3 intMainvoid)4 {5     intbph2o=212;6     intRV;7  8rv=printf ("%d F is water ' s boiling point.\n", BPH2O);9printf"The printf () function printed%d characters.\n", RV);Ten     return 0; One}

5.SCANF () function

(1) scanf () stops reading at the first blank word spaces, tab, or line break. The ~gets () function can be used to read a string.

(2) Read the value of the variable type plus &, and read the string into a character array without using &.

(3) scanf ("%d,%d", &n,&m) accepts input, {scanf ("%c", &ch) reads the first character encountered in the input}

6. About Modifiers *

• • Use * In the field width section in printf () instead of numbers

• • SCANF () * Causes the function to skip the corresponding output item (scanf ("%*d%*d%d", &n) and the first two skips)

　　

1 using variable-width output fields2#include <stdio.h>3 intMainvoid)4 {5 unsigned width,precision;6     intNumber= the;7     Doubleweight=242.5;8 9printf"What field width?\n");Tenscanf"%d",&width); Oneprintf"The number is :%*d:\n", width,number); Aprintf"Now Enter a width and a precision:\n"); -scanf"%d%d",&width,&precision); -printf"weight=%*.*f\n", width,precision,weight); the     return 0; -}

C language string and formatted input and output