Design and plan the logic for a program that prompts the user for and allows the user to enter TWO numbers. The program outputs the sum of the two values. Provide declarations.

To design and plan the logic for a program that prompts the user for two numbers and outputs their sum, we can follow these steps:

Step 1: Declare two variables to store the user's input for the two numbers.
- Let's name them "num1" and "num2".
- The appropriate data type for these variables would be integers, so we will declare them as:
```
int num1;
int num2;
```

Step 2: Prompt the user to enter the first number and store it in the variable "num1".
- To achieve this, you can use a prompt message and then read the user's input using standard input functions.
```
printf("Enter the first number: ");
scanf("%d", &num1);
```

Step 3: Prompt the user to enter the second number and store it in the variable "num2".
- Just like in the previous step, use a prompt message and standard input functions to read the user's input.
```
printf("Enter the second number: ");
scanf("%d", &num2);
```

Step 4: Compute the sum of the two numbers by adding the values stored in "num1" and "num2".
- Create another integer variable to store the sum.
- Use the addition operator to add the values of "num1" and "num2" and assign it to the new variable, let's call it "sum".
```
int sum = num1 + num2;
```

Step 5: Output the sum of the two numbers.
- Print the value of the "sum" variable using standard output functions.
```
printf("The sum of %d and %d is %d.\n", num1, num2, sum);
```

That's it! This logic will prompt the user for two numbers, calculate their sum, and output the result.