• comments begin with /* and end with */

#include <stdio.h>

• is a directive to the C preprocessor.
• lines that begin with # are processed by the preprocessor before the program is compiled.
• the code above tells the preprocessor to include the contents of the standard input/output header (<stdio.h>

int main( void )

• apart of every C program
• the parentheses indicate that main is a program building block called a function
• C programs contain one or more functions, one of which must be main
• int (whole number value)
• void means that main does not return a value

left brace, {, begins the body of every function, ending with a right brace, }. The pair of braces and the portion between is called a block.

printf( "Welcome to C!\n" );

• instructs the computer to perform an action, namely to print the string;
• the string is sometimes called a character string, a message, or a literal
• the entire line is called a statement
• within the parentheses is called an argument
• the semicolon is the statement terminator
• the backslash, \, is an escape character
• \n means new line
• \t means horizontal tab
• \a means alert. sound the system bell.
• \\ backslash. insert backslash character in a string.
• \" double quote. insert double quote character in a string.

• placing variable definitions among executable statements causes syntax errors

scanf( "%d", &integer1 ); /* read an integer */

• scanf is used to obtain a value from the user
• scanf here has two arguments, "%d" and &integer1
  • the first argument, the format control string, indicates the type of data that should be entered by the user; the %d conversion specifier indicates that the data should be an integer (d stands for "decimal integer"); The % in this context is treated by scanf (and printf) as a special character that begins with a conversion specifier
  • the second argument begins with an ampersand called the address operator; denotes where the data is saved

2.5 arithmetic in C

• + addition
• - subtraction
• * multiplication
• / division
• % remainder

• PEMDAS

2.6 Decision Making: equality and relational operators

• x == y "x is equal to y"
• x != y "x is not equal to y"
• x > y "x is greater than y"
• x < y "x is less than y"
• x >= y "x is greater than or equal to y"
• x <= y "x is less than or equal to y"

common error 2.18: confusing the equality operator == with the assignment operator =. To avoid confusion, the equality operator should be read "double equals" and the assignment operator should be read "gets."

calculations can be performed inside printf:

printf ("Sum is %d\n", integer1 + integer2);

the ampersand is not necessary in printf

C's keywords: do not use as identifiers