How to use two characters to control the flow of a c++ program

Question

How do i use two characters (A and B) to control which part of the code is executed when the user enters either of them..? Forexaple when a user Enters A, go to a certain transaction type and ask the user to enter info for that kind of a transaction. If B, execute some other traction type and the user will be asked to enter info for such a transaction. I just started learning programming (C++)please..

Thanks

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The Techel · Answer 1 · 2017-02-04T16:34:56.683

2

C++ as an imperative programming language provides several control statements like if/else, while, switch or for to control the flow of your program. They are explained in your C++-book you're currently reading.

edited Feb 04 '17 at 16:34

answered Feb 04 '17 at 16:25

The Techel

918
8
13

1

*switch/case* seems particularly appropriate for the OP's use case. – Martin Bonner supports Monica Feb 04 '17 at 16:33

score 1 · Accepted Answer · answered Feb 04 '17 at 16:33

Try this.

#include <iostream>

int main() {

    char in;
    std::cin >> in;

    switch (in) {
        case 'A':
            // Do something.
            break;
        case 'B':
            // Do something else.
            break;
        default:
            std::cerr << "Invalid character." << std::endl;
            return 1;
    }

}

Zhou Zhi Hua · Answer 3 · 2017-02-04T17:46:38.670

There are a lot of ways in C++ to achieve selection structure.

if else (basically every programming language have it)

if (a)
{
    //do something
}
else 
{
    //do something else
}

switch control

switch (input)
{
case a:
     // do something
     break;
case b:
     // do something else
     break;
default:
     // default when the user input is not expected a or b
}

labels and goto keyword

int main(void)
{
    //something....
    if (a) goto label_a;
    else if (b) goto label_b;
label_a:
    //something...
    goto end;
label_b:
    //something else
    goto end;
end:    
    return 0;
}

Function calls

void first() { /*something*/ }
void second() { /*something else*/ }

int main(void)
{
    //your previous codes
    if (a) 
    {
        first();
    }
    else
    {
        if (b)
        {
            second();
        }
    }

    return 0;
}

More things to read: CPlusPlus Statements and Controls
Or you can invest some money to buy a good C++ Reference books like C++ Primer

@ThomasMatthews thanks Thomas for pointing out, I'd fixed that. — Zhou Zhi Hua, Feb 04 '17 at 17:41
You could make the `else` with a substatement and put the `if (b)` inside the substatement. — Thomas Matthews, Feb 04 '17 at 17:43

Nils · Answer 4 · 2017-02-04T16:42:54.683

One possible solution is:

#include <iostream>
#include <string>

void input_A() {
    //Do things after input A
    std::cout << "You used function A" << std::endl;
}

void input_B() {
    //Do things after input B
    std::cout << "You used function B" << std::endl;
}

void input_recv(std::string input)
{
    // Use if condition or switch statement for input evaluation
    if (input == "A"){
        input_A();
    }
    else if(input == "B"){
        input_B();
    }
    else {
        std::cout << "No valid input" << std::endl;
    }
}

int main()
{
    std::string input = "";
    std::cout << "Input: ";

    // Wait for input
    std::getline(std::cin, input);

    // Evaluate input
    input_recv(input);

    return 0;
}

score 0 · Answer 5 · answered Feb 04 '17 at 21:06

0

Thanks to this community. A switch/ case control worked for me for now. I am also trying out other controls mentioned here. Thanks everyone who helped...

answered Feb 04 '17 at 21:06

Gonzaga Paul

1
1

How to use two characters to control the flow of a c++ program

5 Answers5