Computer Hardware A computer may be divided into six logical units. Input Unit Obtain information from input devices: keyboards and mouse devices. Place the information at the disposal of the other units to be processed. Output Unit Take information that has been processed. Place it on output devices: displayed on screens, printed on paper. Memory Unit RAM (random access memory) is volatile, stores program and data. ROM (read only memory) is non-volatile, contains fundamental instructions. Arithmetic and Logic Unit (ALU) Perform all the arithmetic and logic operations: addition, subtraction, comparison, etc.. CPU Tell the input unit when information should be read into the memory unit. Tell the ALU when information from the memory should be used in calculations. Tell the output unit when to send information from the memory unit to certain output devices. Secondary Storage. Permanent storage areas for programs and data: magnetic tapes, magnetic hard disks, floppy disk, CD ROM

Computer Software A computer program: set of instructions used to operate a computer to produce a specific result. Computer programming: writing computer programs. Programming languages: languages used to create computer programs. Machine Languages Example: 0101010 000000000001 000000000010 The lowest level of computer languages. Programs consist of entirely of 1s and 0s. Programs can control directly to the computer’s hardware. Machine language instructions consist of two parts:Instruction part (opcode) is the leftmost group of bits and tells the computer the operation to be performed.Address part specifies the memory address of the data to be used in the instruction. Assembly Languages Example: LOAD BASEPAY ADD OVERPAY STORE GROSSPAY Perform the same tasks as machine languages, but use symbolic names for opcodes and operands. An assembly language program must be translated into a machine language program. Translation program (assembler)Machine languageprogramAssembly languageprogram Machine languages and assembly languages are called low-level languages since they are closest to computer hardware. High-level Programming Languages Create computer programs using instructions that much easier to understand: English-like included with mathematical notations. Programs written in high-level languages must be translated into a low level language using a program called a compiler. Each line in a high-level language program is called a statement. Ex: Result = (First + Second)*Third. Application and System Software Application software: perform particular tasks required by the users. System software: must be available to any computer system to operate. The most important system software is the operating system (MS-DOS, UNIX, MS WINDOWS, MS WINDOWS NT) Multitasking systems: operating systems allow user to run multiple programs.