Ohm's Law calculator I'm looking for ways to make this calculator more efficient and/or make the code a little easier to read.

#include &lt;iostream&gt;
#include &lt;cstdlib&gt;
using namespace std;



// variables to be used in the program
double result, valueA, valueB, valA, valB;
int choice;
char cont;

//functions to perform the calculations

double mult(double valueA, double valueB) {
result = valueA * valueB;
return result;
}

double div(double valueA, double valueB) {
result = valueA / valueB;
return result;
}



// functions that prompt the user for values to be calculated


double getValueA(string unit) {
cout &lt;&lt; "Enter " &lt;&lt; unit &lt;&lt; ": " &lt;&lt; endl;
cin &gt;&gt; valA;
cout &lt;&lt; endl;
return valA;
}

double getValueB(string unit) {
cout &lt;&lt; "Enter " &lt;&lt; unit &lt;&lt; ": " &lt;&lt; endl;
cin &gt;&gt; valB;
cout &lt;&lt; endl;
return valB;
}



void title() {
cout &lt;&lt; "**** NEO-VOLT ELECTRICAL CALCULATOR ****" &lt;&lt; endl;
cout &lt;&lt; "*   by *" &lt;&lt; endl;
cout &lt;&lt; "*Adam Pate *" &lt;&lt; endl;
cout &lt;&lt; "****************************************" &lt;&lt; endl;
cout &lt;&lt; endl &lt;&lt; endl &lt;&lt; endl;
}

void showMenu() {
cout &lt;&lt; " Main Menu: " &lt;&lt; endl;
cout &lt;&lt; endl;
cout &lt;&lt; "Ohm's Law" &lt;&lt; endl;
cout &lt;&lt; " 1. Voltage " &lt;&lt; endl;
cout &lt;&lt; " 2. Resistance " &lt;&lt; endl;
cout &lt;&lt; " 3. Current " &lt;&lt; endl;
cout &lt;&lt; "Power Law" &lt;&lt; endl;
cout &lt;&lt; " 4. Wattage " &lt;&lt; endl;
cout &lt;&lt; " 5. Voltage " &lt;&lt; endl;
cout &lt;&lt; " 6. Current " &lt;&lt; endl;
cout &lt;&lt; endl;
cout &lt;&lt; " 0. Exit the program " &lt;&lt; endl;



}
//Shows results of the calculation
void displayResult(string units) {
cout &lt;&lt; result &lt;&lt; " " &lt;&lt; units;
cout &lt;&lt; endl &lt;&lt; endl;

}
// Takes the users choice and calls functions accordingly
void processMenu() {
cin &gt;&gt; choice;
switch(choice) {
case 0:
exit(0);
case 1:
getValueA("Amps");
getValueB("Ohms");
mult(valA, valB);
displayResult("Volts");
break;
case 2:
getValueA("Volts");
getValueB("Amps");
div(valA, valB);
displayResult("Ohms");
break;
case 3:
getValueA("Volts");
getValueB("Ohms");
div(valA, valB);
displayResult("Amps");
break;
case 4:
getValueA("Volts");
getValueB("Amps");
mult(valA, valB);
displayResult("Watts");
break;
case 5:
getValueA("Watts");
getValueB("Amps");
div(valA, valB);
displayResult("Volts");
break;
case 6:
getValueA("Watts");
getValueB("Volts");
div(valA, valB);
displayResult("Amps");
break;
default:
cout &lt;&lt; "Invalid choice.";
}

}




int main()
{
title();
do {
showMenu();
processMenu();
cout &lt;&lt; "Perform another calculation? (y or n)" &lt;&lt; endl;
cin &gt;&gt; cont;
} while(cont != 'n');


return 0;
}
Indent your code.
There is no need to define functions for multiplication and division. It is just as clear to say a * b as mult(a,b).
getValueA and getValueB do exactly the same thing, except with a different global. The return value of these functions is ignored. It would be better to merge these into one and use the return value.
Don't use valA and valB for variable names. Use local variables with names like volt. 
Don't use a global for the result. Pass it as a parameter to displayResult, like this:

case 1:
    double amps = getValue("Amps");
    double ohms = getValue("Ohms");
    displayResult(amps * ohms, "volts");

You can, and should, avoid global variables completely here, as valueA and valueB are never used in the global context, they can be removed.
If the user types "no" or "N" it is treated as Yes. Handle this more carefully. For example, consider only the lowercase of the first letter.