Q:replacing strings without using inbuild functions. We are using gcc compiler and terminal to compile the code and ubuntu OS. PROGRAM: #include<stdio.h> int strln1(char s1[]); int strln2(char s2[]); void strcpy1(char s1[],char s2[]); int main() { char s1[30],s2[30]; int result1,result2; printf("Enter the string s1"); scanf("%s",s1); printf("Enter the string s2"); scanf("%s",s2); printf("Your string s1 is %s",s1); printf("\nYour string s2 is %s",s2); result1=strln1(s1); result2=strln2(s2); printf("\nlength of string s1 is %d\n",result1); printf("\nlength of string s2 is %d\n",result2); strcpy1(s1,s2); } int strln1(char s1[]) { int i,ln; ln=0; i=0; while(s1[i]!='\0') { i++; ln++; } return ln; } int strln2(char