A computer is an electronic device, which can input, process, and output data.
input processing output
A computer Science is the discipline that seeks to build a scientific foundation for such topics as computer design, computer programming, information processing, and algorithmic solutions of problems.
A computer is a machine that stores data, interact with devices, and execute programs (provides computing capabilities to its users).
Primary memory is divided into a number of memory cells (bits) or bytes.
A bit (binary digit) is the smallest storage unit within a computer. It is a tiny electrical circuit that can be in one of two states:
A voltage high represented by the symbol 1
A voltage low represented by the symbol 0
Any system of symbols can be represented by bit or byte patterns.
Each byte has a unique integer address and it is usually 8 bits.
Primary Memory 1,099,511,627,776 40 2 TB Terabyte 1,073,741,824 30 2 GB Gigabyte 1,048,576 20 2 MB Megabyte 1,024 10 2 KB Kilobyte 1 0 2 Byte Number of bytes POWER OF 2 SYMBOL UNIT
Primary and Secondary Memory Comparison Slow Cheap Large capacity Not connected directly to the processor Fast Expensive Low capacity Connects directly to the processor Secondary memory Primary memory
The most important systems program is the operating system.
It is a group of programs that coordinates the operation of all the hardware and software components of the computer system.
It is responsible for starting application programs running and finding the resources that they need.
Examples of operating systems are: Unix, Windows NT, Windows XP, MS-DOS, Linux, Solaris, VMS, OS/2 and System 7.
Computer Languages Computer language evolution The only language understood by a computer is machine language. Note:
Writing, Editing, Compiling, and Linking Programs typical Java environment Primary Memory . . . . . . Disk Disk Disk Editor Compiler Class Loader Program is created in an editor and stored on disk in a file ending with .java . Compiler creates bytecodes and stores them on disk in a file ending with .class . Class loader reads .class files containing bytecodes from disk and puts those bytecodes in memory. Phase 1 Phase 2 Phase 3 Primary Memory . . . . . . Bytecode Verifier Bytecode verifier confirms that all bytecodes are valid and do not violate Java’s security restrictions. Phase 4 Primary Memory . . . . . . Interpreter Interpreter reads bytecodes and translates them into a language that the computer can understand, possibly storing data values as the program executes. Phase 5