C语言常用数字和字符串转换函数(国外英文资料)

C语言常用数字和字符串转换函数(国外英文资料)

C language commonly used Numbers and string conversion functions

The atoi string is converted to integer Numbers

The atol string converts growth integer Numbers

The atof string is converted into a floating-point number

The strtol string converts growth integer Numbers

Strtoul strings are converted to unsigned long integers

Strtod strings are converted into floating point Numbers

Tolower capital letters are converted to lowercase letters

Toupper lowercase letters are converted to capital letters

The toascii integer is converted to a valid ASCII character

Atof: the string is converted to a floating-point number

Related functions atoi, atol, strtod, strtol, strtoul

Header file # include < stdlib. H >

Define function double atof (const char * NPTR);

Functions atof () will scan parameters NPTR string, skip the previous space character, until an digital or plus or minus sign didn't start the conversion, and to meet the Numbers or strings (' \ 0 ') did not end at the end of the transformation, and returns the result. The parameter NPTR string can contain a positive or negative number, a decimal point or E (E) to represent the index portion, such as 123.456 or 123e-2.

The return value returns the number of floating-point Numbers after the transformation.

Additional descriptions of the atof () and the use of strtod ((char * *) NULL); You get the same result.

Example / * concatenated string a and string b into Numbers

# include < stdlib. H >

The main ()

{

Char * a = "-100.65";

Char * b = "200e-2";

Float c;

C = atof (a) + atof (b).

Printf (" c = %. 2f \ n ", c);

}

Execute c = -98.65

Atoi: the string is converted to integer Numbers

Related functions atof, atol, atrtod, strtol, strtoul

Header file # include < stdlib. H >

Define function int atoi (const char * NPTR);

Function atoi () will scan parameters NPTR string, skip the previous space character, until an digital or plus or minus sign didn't start the conversion, and to meet the Numbers or strings ('