C and C character strings

C and C character strings

The C language usually contains characters and strings, while a string or string is actually an array.

Character array Definition

char arr[]={'h','e','l','l','o','\0'};

The defined string:

char arr1[]="HELLO";

The character input and output can use scanf and printf as the one-dimensional array, and the character can also use its own specific input and output functions gerchar and putchar, while using getchar and putchar to input a string of characters

    char arr[1000];    int i=0,j=0;    char ch;    while ((ch=getchar())!='\n') {        arr[i]=ch;        i++;    }    arr[i]='\0';    while (arr[j]!='\0') {        putchar(arr[j]);        j++;    }    printf("\n");

Output result:

Strings also have their own specific input and output functions.

// Input and Output char ch [100]; gets (ch); puts (ch );

 

Function section of the string: the header file needs to be imported.

#include <string.h>

 

Char str1 [30] = "wfds"; char str2 [] = "zfds"; strcpy (str1, str2); // copy str2 to str1, str1 is longer than str2 (str1); puts (str2); strcat (str1, str2); // link str2 to str1, total length space greater than two puts (str1); puts (str2); printf ("len = % lu \ n", strlen (str1 )); // calculate the length of the string printf ("len = % lu \ n", strlen (str2); // do not include '\ 0' printf ("% d \ n ", strcmp (str1, str2 ));

Result:

 

Character functions: the header file needs to be imported.

#include <ctype.h>

 

Char ch = 'A', substring = 'a'; printf ("% d \ n", isalpha (ch )); // whether it is the letter printf ("% d \ n", isupper (ch); // whether it is uppercase printf ("% d \ n", islower (ch )); // whether it is lowercase printf ("% d \ n", isdigit (ch); // whether it is a digital printf ("% c \ n", toupper (ch )); // convert to uppercase printf ("% C \ n", tolower (lower); // convert to lowercase

The string is written in uppercase and lowercase.

    char ch[100],ch1;    gets(ch);    int i=0;    while (ch[i]!='\0') {        ch1=ch[i];        if (isupper(ch1)==1) {           ch1= tolower(ch1);        }else{            ch1=toupper(ch1);        }        putchar(ch1);        i++;    }    printf("\n");

Convert string to integer or floating point type

Header files need to be imported

#include <stdlib.h>

 

// Convert the string to char * chs = "11.52"; printf ("chs = % s \ n", chs); double d = atof (chs ); int a = atoi (chs); printf ("% f \ n", d); printf ("% d \ n", );

Numeric to string

Int num = 1000; char chs [100]; // store num to sprintf (chs, "% d", num) in % d format ); printf ("chs = % s \ n", chs); // stores the sprintf (chs, "% 10 s", "asdf") strings in the specified format "); printf ("chs = % s", chs );