String operation In C++

String operation #include<stdio.h> #include<conio.h> #include<string.h> int STRLEN(char*); int STRCPY(char*,char*); int STRCMP(char*,char*); int STRCAT(char*,char*,char*); int STRREV(char*); void main() { int c; char str[20],str1[10],str2[10],str3[20]; clrscr(); re: printf(" Enter choice=>"); printf(" 1:string len. 2:string copy 3:string cmp. 4:string cat. 5:string rev."); printf(" 6:for exit=>"); scanf("%d",&c);switch(c) { case 1: printf("Enter the string=>"); scanf("%s",&str1); printf("string length=>%d ",STRLEN(str1)); break; case 2: printf(" Enter the string=>"); scanf("%s",str1); STRCPY(str2,str1); printf("copied string=>"); puts(str2); break; case 3: printf("Enter two string=>"); scanf("%s",&str1); scanf("%s",&str2); if(STRCMP(str2,str1)) printf("string is equal"); else printf("String is not equal"); break; case 4: printf("Enter two string=>"); scanf("%s",str1); scanf("%s",str2); STRCAT(str3,str2,str1); puts(str3); break; case 5: printf("Enter the string=>"); scanf("%s",str1); STRREV(str1); printf("Reverse stringis=>"); puts(str1); break; default: goto end; } goto re; end: getch(); } int STRLEN(char *s) { int i=0; while(*s!=NULL) { i++; s++; } return i; } int STRCPY(char *s2,char *s1) { while(*s1!=NULL) { *s2=*s1; s2++; s1++; } *s2=NULL; return 1; } int STRCMP(char *s2,char *s1) { int i=0,len1,len2; len1=strlen(s1); len2=strlen(s2); if(len1==len2) { while(*s2==*s1 && *s2 != NULL && *s1!=NULL) { i++; s1++; s2++; } if(i==len1) return 1; else return 0; } else { return 0; } } int STRREV(char *s) { int len; char *s1; char *ptr; len=strlen(s); s1=(char *)malloc(sizeof(char)); strcpy(s1,s); ptr=s1+len-1; while(*s!=NULL) { *s=*ptr; ptr--; s++; s1++; } *s=NULL; return 1; } int STRCAT(char *s3,char *s2,char *s1) { while(*s1!=NULL) { *s3=*s1; s3++; s1++; } s3++; while(*s2!=NULL) { *s3=*s2; s3++; s2++; } *s3=NULL; return 1; }