Question

The following program has syntax mistakes. Correct them. On each successive line, assume that any preceding error has been corrected. const char = STAR = '*' const int PRIME = 71; int main { int count, sum; double x; count = 1; sum = count + PRIME; x := 25.67; newNum = count * ONE + 2; sum + count = sum; x = x + sum * COUNT; cout << " count = " << count << ", sum = " << sum << ", PRIME = " << Prime << endl; }

Short answer

Correct the syntax for constants and variable declarations, use `=`, initialize undeclared variables, and correct capitalization and expressions.

Step-by-step solution

Correct constant declaration

The first line uses the wrong syntax for declaring constants in C++. Correct the syntax to use the correct type definition: Incorrect: `const char = STAR = '*'` Corrected: `const char STAR = '*'`.

Correct main function declaration

The `main` function needs parentheses to indicate it takes no parameters. Incorrect: `int main` Corrected: `int main()`.

Correct assignment operator

In line 7, the assignment operator should be `=` instead of `:=`. Incorrect: `x := 25.67;` Corrected: `x = 25.67;`.

Declare and initialize uninitialized variables

The variable `newNum` and `ONE` needs to be declared and initialized since they're not previously defined: Add before usage: `const int ONE = 1;` Incorrect `newNum = count * ONE + 2;` will work correctly after the above addition.

Correct sum expression

Line `sum + count = sum;` is invalid because the left side of an assignment should be a single variable, not an expression. Corrected: `sum = sum + count;`.

Remove undefined variable

The variable `COUNT` in `x = x + sum * COUNT;` is not defined. Assuming COUNT is synonymous with `count`, it should be replaced. Corrected: `x = x + sum * count;`.

Fix string output

In the `cout` statement, the variable `Prime` is incorrectly capitalized and should match `PRIME`. Incorrect: `<< "PRIME = " << Prime << endl;` Corrected: `<< "PRIME = " << PRIME << endl;`.

Key concepts

Constant Declaration

In C++, constants are fixed values that, once defined, cannot be changed during the execution of a program. This means they are immutable. Constants are typically used to define values that are reused throughout a program and remain unchanged.

To declare a constant, the `const` keyword is used, followed by the data type and the initial value. The syntax is:

• `const data_type constant_name = value;`

In the exercise example, the constant was incorrectly defined as `const char = STAR = '*'`, where the placement of the `=` sign was wrong.

The corrected line is: `const char STAR = '*'`, making `STAR` an immutable character variable with the value '*'. This type of declaration ensures that any attempt to change the value of `STAR` elsewhere in the code will cause an error.

Main Function

The `main` function is the entry point for any C++ program. It's essentially where the program begins execution.

Every C++ application must include the `main` function. Its correct syntax is:

• `int main()`

The parentheses `()` following `main` indicate that this function does not take any parameters. In the example, `int main` was missing these parentheses, which would lead to a syntax error, as the function signature was incomplete.

Fixing it to `int main()` resolves this issue, ensuring that the program can start correctly when compiled and run.

Assignment Operator

The assignment operator in C++ is represented by the equals sign `=`. It is used to assign a value to a variable.

For example, in the statement `x = 25.67;`, the value `25.67` is assigned to the variable `x`. It's crucial to use the correct assignment operator to avoid syntax errors. In some programming languages, like Pascal, `:=` is used for assignment, but in C++, it must be `=`.

In the given exercise, the incorrect Line `x := 25.67;` was corrected to `x = 25.67;`. Using the proper syntax for operators ensures smooth program execution without unexpected errors.

Variable Declaration

In C++, variables must be declared before they are used in a program. Declaring a variable involves specifying its type, followed by its name.

The basic syntax is:

• `data_type variable_name;`

For instance, declaring an integer variable might look like `int count;`, while for a double, it would be `double x;`. It's also a good practice to initialize variables upon declaration when possible.

In the provided exercise, the variable `newNum` was used without being declared, and the constant `ONE` also needed declaration and initialization. To fix this, `const int ONE = 1;` should be added before `newNum` is calculated, thus ensuring all variables are declared and initialized before use.

This prevents errors and ambiguities, making the code robust and clear.