Computer Science Chapter1-4

• Computers process data under the control of instructions called Program
• A computer's key logical units


  • input unit
  • output unit
  • memory unit
  • central processing
  • arithmetic unit
  • logic unit
  • secondary storage unit
• Types of programming languages discussed in the chapter

  • machine languages
  • assembly languages
  • high-level languages
• Compilers


  Programs that translate high-level-language programs into machine language
• Android is an operating system for mobile devices based on the Linux kernel
• An acceleromoter allows a device to respond to motion
• C is widely known as the language of the UNIX operating system
• C programs


  Normally typed into a computer using an editor
• C program compilation process

  1. Preprocessor executes

  2. Translation phase

  3. Linker combines output of compiler with library functions

  4. Loader transfers executable image from disk to memory
• C


  • Facilitates a structured and disciplined approach to computer-program design
• Comments


  Document programs and improve program readability
• Comments are ignored by the compiler
• Preprocessor


  Processes lines beginning with # before the program is compiled
• #include directive


  Tells the preprocessor to include the contents of another file
• <stdio.h> header


  Contains information used by the compiler to ensure correct use of standard input/output library functions, such as printf
• main function


  Part of every program, where the program begins executing
• int


  Indicates that main "returns" an integer (whole number) value
• void


  Indicates that main does not receive any information
• Left brace {


  Begins every function's body
• Right brace }


  Ends each function
• Block


  A pair of braces and the code between them
• printf function


  Instructs the computer to display information on the screen
• String


  Sometimes called a character string, a message or a literal
• Statement


  Must end with the semicolon statement terminator
• Escape character \


  When encountering a backslash in a string, the compiler combines it with the next character to form an escape sequence
• Escape sequence \n


  Means newline
• Escape sequence \\


  Places a single backslash in a string
• Escape sequence \"


  Represents a literal double-quote character
• Variable


  A location in memory where a value can be stored for use by a program
• int


  Holds whole-number integer values
• Identifier


  A series of characters consisting of letters, digits and underscores ( _ ) that does not begin with a digit
• C is case sensitive
• scanf function


  Gets input from the standard input—usually the keyboard
• scanf format control string

  Indicates the type(s) of data to input
• %d conversion specification


  Indicates an integer (the letter d stands for "decimal integer")
• Address operator &


  Tells scanf the variable's memory location
• Assignment statement


  Most calculations are performed in
• Binary operators


  = and + each have two operands
• printf format control string


  Conversion specifications indicate placeholders for data to output
• Destructive


  When a value is placed in a memory location, it replaces the location's previous value, which is lost