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A computer program is a sequence of instructions that tell the computer what to do.
Statements and expressions
The most common type of instruction in a program is the statement. A statement in C++ is the smallest independent unit in the language. In human language, it is analogous to a sentence. We write sentences in order to convey an idea. In C++, we write statements in order to convey to the compiler that we want to perform a task. Statements in C++ are terminated by a semicolon.
There are many different kinds of statements in C++. The following are some of the most common types of simple statements:
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int x;
x = 5;
cout << x;
int x is a declaration statement. It tells the compiler that x is a variable. All variables in a program must be declared before they are used. We will talk more about variables shortly.
x = 5 is an assignment statement. It assigns a value (5) to a variable (x).
cout << x; is an output statement. It outputs the value of x (which we set to 5 in the previous statement) to the screen.
The compiler is also capable of resolving expressions. An expression is an mathematical entity that evaluates to a value. For example, in math, the expression 2+3 evaluates to the value 5. Expressions can involve values (such as 2), variables (such as x), operators (such as +) and functions (which return an output value based on some input value). They can be singular (such as 2, or x), or compound (such as 2+3, 2+x, x+y, or (2+x)*(y-3)).
For example, the statement x = 2 + 3; is a valid assignment statement. The expression 2+3 evaluates to the value of 5. This value of 5 is then assigned to x.
Functions
In C++, statements are typically grouped into units called functions. A function is a collection of statements that executes sequentially. Every C++ program must contain a special function called main(). When the C++ program is run, execution starts with the first statement inside of main(). Functions are typically written to do a very specific job. For example, a function named Max() might contain statements that figures out which of two numbers is larger. A function named CalculateGrade() might calculate a student
Statements and expressions
The most common type of instruction in a program is the statement. A statement in C++ is the smallest independent unit in the language. In human language, it is analogous to a sentence. We write sentences in order to convey an idea. In C++, we write statements in order to convey to the compiler that we want to perform a task. Statements in C++ are terminated by a semicolon.
There are many different kinds of statements in C++. The following are some of the most common types of simple statements:
1
2
3
int x;
x = 5;
cout << x;
int x is a declaration statement. It tells the compiler that x is a variable. All variables in a program must be declared before they are used. We will talk more about variables shortly.
x = 5 is an assignment statement. It assigns a value (5) to a variable (x).
cout << x; is an output statement. It outputs the value of x (which we set to 5 in the previous statement) to the screen.
The compiler is also capable of resolving expressions. An expression is an mathematical entity that evaluates to a value. For example, in math, the expression 2+3 evaluates to the value 5. Expressions can involve values (such as 2), variables (such as x), operators (such as +) and functions (which return an output value based on some input value). They can be singular (such as 2, or x), or compound (such as 2+3, 2+x, x+y, or (2+x)*(y-3)).
For example, the statement x = 2 + 3; is a valid assignment statement. The expression 2+3 evaluates to the value of 5. This value of 5 is then assigned to x.
Functions
In C++, statements are typically grouped into units called functions. A function is a collection of statements that executes sequentially. Every C++ program must contain a special function called main(). When the C++ program is run, execution starts with the first statement inside of main(). Functions are typically written to do a very specific job. For example, a function named Max() might contain statements that figures out which of two numbers is larger. A function named CalculateGrade() might calculate a student