Running the below code it by default takes the value on its own after I choose the option from 1-5 (don't forget see the last portion for deatils) [duplicate]

See more:

C

string

#include<stdio.h>
#include<string.h>

void len();// function declaration
void cpy();// function declaration
void cat();// function declaration
void cmp();// function declaration
void rev();// function declaration

void main()    
{    
    int n;

    printf(" 1.Find length of string.\n 2.Copy one string to another.\n 3.Append one string to another.\n 4.Compare two strings.\n 5.Reverse one string\n");

    printf("\nChoose your string option:");   
    scanf("%d",&n);

    printf("\n"); 

    switch(n) {
      case 1: 
        len(); //function call
        break;
      case 2:
        cpy();//function call
        break;
      case 3:
        cat();//function call
        break;
      case 4:
        cmp();//function call
        break;
      case 5:
        rev();//function call
        break;
      default:
        printf("ERROR,Wrong Input!\n");
    }
}
   
void len() // function definition     
{   
    char a[10];
    int a1;
    
    printf("enter a string:");
    gets(a);
    
    a1=strlen(a);// strlen is a string manipulation function for finding the length of the string.
    
    printf("The length of the string is %d",a1);
}    

void cpy() // function definition 
{
    char str1[10],str2[10];
    
    printf("Enter String=");
    gets(str1);
    
    strcpy(str2,str1);      
    printf("The given string is %s",str2);
}
    
void cat() // function definition 
{
    char str1[10],str2[10];
    
    printf("Enter string 1=");        
    gets(str1);
    
    printf("Enter string 2=");       
    gets(str2);
    
    strcat(str1,str2);      
    printf("The New appended String is %s",str1); 
}    

void cmp() // function definition 
{
    char str1[10],str2[10];
    
    printf("Enter string 1=");
    gets(str1);
    
    printf("Enter string 2=");
    gets(str2);

    if(!strcmp(str1,str2)) {
        printf("STRINGS ARE EQUAL");
    } else {
        printf("STRINGS ARE NOT EQUAL");
    }
}   

void rev() // function definition    
{
    char str[10];
    printf("Enter string 1=");
    gets(str);
    strrev(str);
    printf("The reversed string is : %s",str);
}

What I have tried:

So when i run the above code , then in the output screen when i choose any of the option(1-5) it took the other input details required to provide(for eg: i have to input a string to find the length of that string on it's own and show the output without i even entering a string : this is the pic of output problem i am getting :

another output screen with diffrent values

I have also run the same string manipulation function individually in a code , it works fine , and i get all my desired output without any other problem, but when i run this above code all the string manipulation function all together i get problems in my output.