11 The System Unit Electronic circuitry within the computer cabinet
12 The System Unit Two general parts Central Processing Unit (CPU) - an integrated micro- circuit that translates data into information
13 The CPU consists of : u Control Unit (CU) u Arithmetic and Logical Unit (ALU) u Some Registers.
14 The Control Unit (CU) within a CPU coordinates all activities of the computer by determining which operations to perform and in what order to carry them out. The CU transmits coordinating control signals to other computer components.
15 The ALU consists of electronic circuitry to perform arithmetic operations (addition, subtraction, multiplication and division), logical operations (and, or, not, …) and to make some comparisons (less-than, equal, … etc.)
16 The System Unit Two general parts Memory - referred to as primary storage or random access memory (RAM), it temporarily holds data and programs for use during processing ( volatile )
17 RAM RAM consists of locations or cells. Each cell has a unique address which distinguishes it from other cells.
Main Memory Address Memory locations 123n123n Memory Cell
23 Common Secondary Media Diskettes –Data represented as magnetic spots on removable flexible plastic disks –Most common size is 3 1/2 inches, in a rigid plastic case –Disk drive holds the diskette, reads or retrieves the data and writes or stores data
24 Common Secondary Media Hard drive –Data is represented magnetically as with diskettes –Normally more than one rigid platter in a sealed unit –These disks are not removable –Significantly more capacity and faster operating than diskettes
26 Output Devices Pieces of equipment that translate the processed information from the CPU into a form that humans can understand.
27 Output Devices u Monitors u Printers F Dot matrix printers F Ink jet printers F Laser printers u Sound plasters u Controlling other devices
28 Communications Devices Hardware that sends and receives data and programs from one computer or secondary storage device to another.
29 Units of Measurements Bit (Binary Digit)(takes two values: 1 or 0) Bit (Binary Digit)(takes two values: 1 or 0) Byte = 8 bits Byte = 8 bits KB (Kilo-byte) = 1024 bytes KB (Kilo-byte) = 1024 bytes MB (mega-byte) = 1024 KB MB (mega-byte) = 1024 KB GB (giga-byte) = 1024 MB GB (giga-byte) = 1024 MB TB (Tera-byte) = 1024 GB TB (Tera-byte) = 1024 GB
30 Connectivity The computer’s capability to send and receive information from other locations.
31 Systems of interconnected computers, known as networks, are the sources of distant information. Connectivity
32 Systems of interconnected computers, known as networks, are the sources of distant information. The National Information Infrastructure (NII) is currently the Internet. Connectivity
33 Computer Viruses A computer virus is an application program designed and written to destroy other programs. - It has the ability to: u Link itself to other programs u Copy itself (it looks as if it repeats itself)
34 Examples of Viruses n Monkes n ABC n Crabs n CIH
35 How do you know if you have a virus? Lack of storage capability Lack of storage capability Decrease in the speed of executing programs Decrease in the speed of executing programs Unexpected error messages Unexpected error messages Halting the system Halting the system
Protection against Computer Viruses Buy original copies of software only Buy original copies of software only Make backups of your files Make backups of your files Do not let any body to insert a diskette in your computer unless you are sure they do not have any viruses. Do not let any body to insert a diskette in your computer unless you are sure they do not have any viruses. Write-protect your disks Write-protect your disks Use anti-virus programs Use anti-virus programs