ช่วยผมหน่อยครับกรุณาช่วยดูและแก้ใขไห้หน่อยนะครับ

ผมจะทำโปรแกรมทีมันรวมหลายๆๆโปรแกรมแต่ มันมีปํญหาเมนู กับการเลือกไป ทำโปรแกรมย่อยต่างๆๆ ผมไม่รู้จะใช้วิธีไหนที่พอกดตัวเลือกไห้ตรงกับเมนูแล้ว ไปทำงานในโปรแกรมย่อยๆๆนั้น และ ผม ยังทำเมนูกลับไปเมนูหลังยังไม่ได้เลยครับ ช่วยแก้ใขไห้หน่อยนะครับ

#include <stdio.h>
#include <conio.h>
#define pi 3.14159

Positive();
Delete();
Multiply();
Divide();
kd();
dk();
pk();
kp();
mk();
km();
square();
triangle();
circle();
volume();

main()
{
char answer;

clrscr();

printf("Positive = 1 \n ");
printf("Deletem = 2 \n ");
printf("Multiply = 3 \n ");
printf("Divide() = 4 \n ");
printf("Kevin>degrees = 5 \n ");
printf("degrees>Kevin = 6 \n ");
printf("Pounds>kilograms = 7 \n ");
printf("kilograms>Pounds = 8 \n ");
printf("Miles>kilometers = 9 \n ");
printf("kilometers>Miles = 10 \n ");
printf("square = 11 \n ");
printf("triangle = 12 \n ");
printf("circle = 13 \n ");
printf("volume = 14 \n ");

answer = getchar();
if(answer=='1')
Positive();
if(answer=='2')
Delete();
if(answer=='3')
Multiply();
if(answer=='4')
Divide();
if(answer=='5')
kd();
if(answer=='6')
dk();
if(answer=='7')
pk();
if(answer=='8')
kp();
if(answer=='9')
mk();
if(answer=='a')
km();
if(answer=='b')
square();
if(answer=='c')
triangle();
if(answer=='d')
circle();
if(answer=='e')
volume();
else
printf("/n");

}


Positive()
{

float ans;
float num;
float num1;

printf("Input ");
scanf ("%f",&num);
printf("Input ");
scanf ("%f",&num1);
ans=num+num1;
printf("ans=%.2f",ans);

}

Delete()
{
float ans;
float num;
float num1;

printf("Input ");
scanf ("%f",&num);
printf("Input ");
scanf ("%f",&num1);

ans=num-num1;
printf("ans=%.2f",ans);


}

Multiply()
{
float ans;
float num;
float num1;

printf("Input ");
scanf ("%f",&num);
printf("Input ");
scanf ("%f",&num1);

ans=num*num1;
printf("ans=%.2f",ans);
}

Divide()
{
float ans;
float num;
float num1;

printf("Input ");
scanf ("%f",&num);
printf("Input ");
scanf ("%f",&num1);

ans=num/num1;
printf("ans=%.2f",ans);

}

kd()
{
float ans;
float num;
float num1;

printf("Input K. ");
scanf ("%f",&num);




ans=num-273.15;
printf("ans %.2fC.",ans);

}

dk()
{
float ans;
float num;
float num1;
printf("Input C. ");
scanf ("%f",&num);

ans=num+273.15;
printf("ans %.2fK.",ans);

}

pk()
{
float ans;
float num;
float num1;


printf("Input pound ");
scanf ("%f",&num);




ans=num*0.45359;
printf("ans %.2fKG.",ans);

}


kp()
{
float ans;
float num;
float num1;


printf("Input KG. ");
scanf ("%f",&num);




ans=num*2.2046;
printf("pound ans= %.2fP.",ans);

}

mk()
{
float ans;
float num;
float num1;


printf("Input mile ");
scanf ("%f",&num);




ans=num*1.6093;
printf("Kilometer ans= %.2fKM.",ans);

}

km()
{
float ans;
float num;
float num1;

printf("Input meter ");
scanf ("%f",&num);




ans=num/1.6093;
printf("mile ans= %.2f",ans);

}


square()
{

float ans;
float wide;
float long1;
char me;


printf("Input wide ");
scanf ("%f",&wide);
printf("Input long");
scanf ("%f",&long1);

ans=wide*long1;
printf("ans=%f \n" ,ans);
printf("go menu 1 exit 2 \n");

scanf("%d",me);
if(me=='1')
main();
else
printf("\n");



}

triangle()
{
float ans,ans1;
float High;
float long1;

printf("Input High ");
scanf ("%f",&High);
printf("Input long");
scanf ("%f",&long1);

ans=High*long1;
ans1=ans/2;

printf("ans1=%f",ans1);


}

circle()
{

float radius;
printf("Enter circle radius : ");
scanf("%f",&radius);

printf("Area of circle = %.2f\n", pi*radius*radius);
printf("Circumference of circle = %.2f\n", 2*pi*radius);

}

volume()
{
float radius;
float high;
printf("Enter circle radius : ");
scanf("%f",&radius);
printf("Enter high : ");
scanf("%f",&high);

printf("Volume of a cylinder= %.2f\n", pi*radius*radius*high);

}