How to solve Error : else without a previous if [closed] - c

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I've been trying to solve this error for half an hour now.
How do I get this code to work?
Here's the input, please point out my mistake(s).
#include <stdio.h>
#include <math.h>
void main()
{
const float pi = 3.142;
int choice;
float radius, volume, volts, ohms, watts, mass, accel, force;
printf("\n1. Calculate the volume of a sphere");
printf("\n2. Calculate the power of a circuit");
printf("\n3. Calculate the force of an object");
printf("\n-----------------------------------\n");
printf("What is your choice? : ");
scanf("%d", &choice);
if(choice==1)
printf("Enter value of radius (cm) : ");
scanf("%f", &radius);
volume = 4/3 * pi * pow(radius,3);
printf("Volume of a sphere is %.2f", volume);
else if(choice==2)
printf("Enter value of voltage (volts) : ");
scanf("%f", &volts);
printf("Enter value of resistance (ohms) : ");
scanf("%f", &ohms);
watts = pow(volts,2) / ohms;
printf("Power of circuit is : %.2f watts", watts);
else if(choice==3)
printf("Enter mass of object (kg) : ");
scanf("%f", &mass);
printf("Enter acceleration (meters per second squared) : ");
scanf("%f", &accel);
force = mass * accel;
printf("The force of the object is : %.2f Neutons", force);
else
printf("You've entered an invalid choice...");
getch();
}

Answer 1

Use braces if a if/else block has multiple lines:
if (choice==1) {
printf("Enter value of radius (cm) : ");
scanf("%f", &radius);
volume = 4/3 * pi * pow(radius,3);
printf("Volume of a sphere is %.2f", volume);
} else if (choice==2) {
printf("Enter value of voltage (volts) : ");
scanf("%f", &volts);
printf("Enter value of resistance (ohms) : ");
scanf("%f", &ohms);
watts = pow(volts,2) / ohms;
printf("Power of circuit is : %.2f watts", watts);
} else if (choice==3) {
printf("Enter mass of object (kg) : ");
scanf("%f", &mass);
printf("Enter acceleration (meters per second squared) : ");
scanf("%f", &accel);
force = mass * accel;
printf("The force of the object is : %.2f Neutons", force);
} else printf("You've entered an invalid choice...");
Without braces your code is interpreted like
// Standalone if block
if (choice==1)
printf("Enter value of radius (cm) : ");
// End of the if block
// ...
// else without previous if (syntax error)
else if (choice==2)
printf("Enter value of voltage (volts) : ");

Answer 2

Use if..else if..else block properly with braces.
If you are using GCC compiler then use following code and compile code with math library.
For example (correct way): gcc test.c -lm
otherwise it gives error : undefined reference to 'pow' (math library function)
#include <stdio.h> //Standard IO functions
#include <math.h> //math functions
int main()
{
const float pi = 3.142;
int choice;
float radius, volume, volts, ohms, watts, mass, accel, force;
printf("\n1. Calculate the volume of a sphere");
printf("\n2. Calculate the power of a circuit");
printf("\n3. Calculate the force of an object");
printf("\n-----------------------------------\n");
printf("What is your choice? : ");
scanf("%d", &choice);
if(choice==1)
{
printf("Enter value of radius (cm) : ");
scanf("%f", &radius);
volume = 4/3 * pi * pow(radius,3);
printf("Volume of a sphere is %.2f", volume);
}
else if(choice==2)
{
printf("Enter value of voltage (volts) : ");
scanf("%f", &volts);
printf("Enter value of resistance (ohms) : ");
scanf("%f", &ohms);
watts = pow(volts,2) / ohms;
printf("Power of circuit is : %.2f watts", watts);
}
else if(choice==3)
{
printf("Enter mass of object (kg) : ");
scanf("%f", &mass);
printf("Enter acceleration (meters per second squared) : ");
scanf("%f", &accel);
force = mass * accel;
printf("The force of the object is : %.2f Neutons", force);
}
else
printf("You've entered an invalid choice...");
return 0;
}

Answer 3

missing brackets in if else command
#include <stdio.h>
void main()
{
const float pi = 3.142;
int choice;
float radius, volume, volts, ohms, watts, mass, accel, force;
printf("\n1. Calculate the volume of a sphere");
printf("\n2. Calculate the power of a circuit");
printf("\n3. Calculate the force of an object");
printf("\n-----------------------------------\n");
printf("What is your choice? : ");
scanf("%d", &choice);
if(choice==1)
{
printf("Enter value of radius (cm) : ");
scanf("%f", &radius);
volume = 4/3 * pi * pow(radius,3);
printf("Volume of a sphere is %.2f", volume);
}
else if(choice==2)
{
printf("Enter value of voltage (volts) : ");
scanf("%f", &volts);
printf("Enter value of resistance (ohms) : ");
scanf("%f", &ohms);
watts = pow(volts,2) / ohms;
printf("Power of circuit is : %.2f watts", watts);
}
else if(choice==3)
{
printf("Enter mass of object (kg) : ");
scanf("%f", &mass);
printf("Enter acceleration (meters per second squared) : ");
scanf("%f", &accel);
force = mass * accel;
printf("The force of the object is : %.2f Neutons", force);
}
else
printf("You've entered an invalid choice...");
getch();
}

Answer 4

You are missing the curly braces {}.
Do: if() { ... } else if() { ...}. You should take a look at: if statement without brackets