Strcpy,strcmp,strlen,strcat function prototype in C language

//strcat (DEST,SRC) adds the string src refers to at the end of the Dest (overwrites the ' + ' at the end of the dest) and adds ' % 'Char*strcat (Char* Strdest,Const Char*strsrc) {    Char*res=strdest; Assert ((strdest!=null) && (strsrc!=NULL));  while(*strdest) strdest++;  while(*strdest=*strsrc) {strdest++; STRSRC++; }    returnRes;}//strcpy (DEST,SRC) copies a string with a null terminator starting from the SRC address to an address space starting with destChar*strcpy (Char*strdest,Const Char*strsrc) {    Char*res=strdest; Assert ((strdest!=null) && (strsrc!=NULL));  while(*strdest=*strsrc) {strdest++; STRSRC++; }    returnRes;}

Today to Evans Innovation interview, The Examiner asked me a simple implementation, that is: the implementation of their own writing STRCPM, IBM has also written strcpy prototype, these functions in the interview is often tested, very representative, and suddenly was asked to be really a bit unprepared. Now write down for everyone to study and later review: (the following procedure by myself)

1. The Strcat function prototype is as follows:
Char *strcat (char *strdest, const char *STRSCR)//Adds the source string to const, indicating that it is an input parameter
{
char * address = strdest; If the statement is placed after the Assert, the compilation error
ASSERT ((strdest! = null) && (STRSCR! = null)); Add a non-0 assertion to the source address and destination address
while (*strdest)//is a simplified form of while (*strdest!= '/0 ')
{//if using while (*strdest++), an error occurs because + + is not subject to looping
strdest++; Constrained. So be in the loop body + +; Because if *strdest last point
}//To the end flag of the string '/0 '.
while (*strdest++ = *strscr++)
{
NULL; The cycle condition can be used in + +,
}//Here you can add the statement *strdest= '/0 '; Is there any need?
return address; To implement chained operations, return the destination address
}
The following is an example of debugging in VC6.0, where the function name is replaced with Strcata.
#include <stdio.h>
#include <assert.h>
Char *strcata (char *strdest,const char *strscr)
{
char * address = strdest;
ASSERT ((strdest! = null) && (STRSCR! = null));
while (*strdest)
{
strdest++;
}
while (*strdest++ = *strscr++)
{
NULL;
}
return address;
}

void Main ()
{
Char str1[100]={"I Love"};
Char str2[50]={"China"};
printf ("%s/n", Strcata (STR1,STR2));
}
2. The strcpy function prototype is as follows:
Char *strcpy (char *strdest, const char *STRSCR)
{
Char *address=strdest;
ASSERT ((strdest! = null) && (STRSCR! = null));
while (*STRSCR)//is a simplified form of while (*strscr! = '/0 ');
{
*strdest++ = *strscr++;
}
*strdest = '/0 '; When the STRSCR string length is less than the original strdest string length
return address; , if you do not change the statement, you will get an error.
}
The following is an example of debugging in VC6.0, where the function name is replaced with Strcpya.
#include <stdio.h>
#include <assert.h>
Char *strcpya (char *strdest, const char *STRSCR)
{
char *address = strdest;
ASSERT ((strdest! = null) && (STRSCR! = null));
while (*STRSCR)
{
*strdest++ = *strscr++;
}
*strdest = '/0 ';
return address;
}

void Main ()
{
Char str1[100]={"I Love"};
Char str2[50]={"China"};
printf ("%s/n", Strcpya (STR1,STR2));
}
3. The STRCMP function prototype is as follows:
int strcmp (const char *str1,const char *STR2)
{
int len = 0;
ASSERT ((str1! = '/0 ') && (str2! = '/0 '));
while (*str1 && *str2 && (*str1 = = *STR2))
{
str1++;
str2++;
}
return *STR1-*STR2;
}
The following is an example of debugging in VC6.0, where the function name is replaced with Strcmpa.
#include <stdio.h>
#include <assert.h>
int Strcmpa (const char *str1,const char *STR2)
{
int len = 0;
ASSERT ((str1! = '/0 ') && (str2! = '/0 '));
while (*str1 && *str2 && (*STR1==*STR2))
{
str1++;
str2++;
}
return *STR1-*STR2;
}

void Main ()
{
Char str1[100] = {"I Love"};
Char str2[50] = {"China"};
printf ("%d/n", Strcmpa (STR1,STR2));
}
4. The Strlen function prototype is as follows:
int strlen (const char *STR)
{
int len = 0;
ASSERT (str = NULL);
while (*str++)
{
len++;
}
return Len;
}
The following is an example of debugging in VC6.0, where the function name is replaced with Strlena.
#include <stdio.h>
#include <assert.h>
int Strlena (const char *STR)
{
int len = 0;
ASSERT (str = NULL);
while (*str++)
{
len++;
}
return Len;
}
void Main ()
{
Char str1[100] = {"I Love"};
Char str2[50] = {"China"};
printf ("%d/n", Strlena (STR1));
}

Strcpy,strcmp,strlen,strcat function prototype in C language