Introduction to Programming

Key terms  CPU  I/O Devices  Main memory  Secondary memory  Operating system  User interface  Application  GUI  Digital  Binary  Memory address  Volatile  RAM  ROM Hint: You will see these again in a quiz soon.

 Hardware Monitor CPU Hard drive Mouse Keyboard DVD-ROM Power Supply  Software Operating system ○ Windows XP ○ Mac OS ○ Linux Applications ○ Word ○ Outlook express ○ Photoshop ○ Firefox

Central Processing Unit  Uses the main memory  Performs all the basic processing in a computer  Reads and executes instructions  Made up of the control unit, registers, and arithmetic/logic unit Central Processing Unit Main Memory

Input/Output Devices  Input Devices Mouse Keyboard Scanner Microphone Hard drive (any file)  Output Devices Monitor Speakers Printer Hard drive (any file)

Secondary Memory Central Processing Unit Main Memory Floppy Disk Hard Disk Secondary memory devices provide long-term storage Information is moved between main memory and secondary memory as needed Hard disks Floppy disks ZIP disks Writable CDs Writable DVDs Tapes

© 2004 Pearson Addison-Wesley. All rights reserved1-7 Software Categories  Operating System controls all machine activities provides the user interface to the computer manages resources such as the CPU and memory Windows XP, Unix, Linux, Mac OS  Application program generic term for any other kind of software word processors, missile control systems, games  Most operating systems and application programs have a Graphical User Interface (GUI)

Digital vs. Analog  Digital Uses 0 or 1 Binary Number System  Analog Anything that can change gradually Example: Temperature

Representing Text Digitally H i, H e a t h e r

Bytes and Bits  A bit is one unit of info – a 1 or a 0  A byte is 8 units of info –  A megabyte (MB) is 1 million bytes or basically 8 million bits

© 2004 Pearson Addison-Wesley. All rights reserved1-13 Memory Main memory is divided into many memory locations (or cells) Each memory cell has a numeric address, which uniquely identifies it

© 2004 Pearson Addison-Wesley. All rights reserved1-14 Storing Information Large values are stored in consecutive memory locations Each memory cell stores a set number of bits (usually 8 bits, or one byte)

© 2004 Pearson Addison-Wesley. All rights reserved1-15 Storage Capacity  Every memory device has a storage capacity, indicating the number of bytes it can hold  Capacities are expressed in various units: KB2 10 = 1024 MB2 20 (over 1 million) GB2 30 (over 1 billion) TB2 40 (over 1 trillion) UnitSymbolNumber of Bytes kilobyte megabyte gigabyte terabyte

© 2004 Pearson Addison-Wesley. All rights reserved1-16 Memory  Main memory is volatile - stored information is lost if the electric power is removed  Secondary memory devices are nonvolatile  Main memory and disks are direct access devices – all information is directly accessible  The terms direct access and random access often are used interchangeably  A magnetic tape is a sequential access device since its data is arranged in a linear order - you must get past the intervening data in order to access other information

© 2004 Pearson Addison-Wesley. All rights reserved1-17 RAM vs. ROM  RAM - Random Access Memory (direct access)  ROM - Read-Only Memory  The terms RAM and main memory are basically interchangeable  ROM could be a set of memory chips, or a separate device, such as a CD ROM  Both RAM and ROM are random (direct) access devices!  RAM probably should be called Read-Write Memory (but it usually isn’t)

© 2004 Pearson Addison-Wesley. All rights reserved1-18 The Central Processing Unit  A CPU is on a chip called a microprocessor  It continuously follows the fetch-decode-execute cycle: fetch Retrieve an instruction from main memory decode Determine what the instruction is execute Carry out the instruction

© 2004 Pearson Addison-Wesley. All rights reserved1-19 The Central Processing Unit  The CPU contains: Arithmetic / Logic Unit Registers Control Unit Small, expensive storage areas Performs calculations and makes decisions Coordinates processing steps