Computer Science

High and low level languages. What is a computer program? A computer program is a collection of instructions that can be executed by a computer to perform a specific task. High level language. A high-level language ( HLL ) is a programming language such as  C ,  FORTRAN , or  Pascal  that enables a programmer to write programs that are more or less independent of a particular type of computer. Such languages are considered high-level because they are closer to human languages and further from  machine languages . Examples. Python, Visual Basic, Delphi, Perl, PHP, ECMAScript, Ruby, C#,  Java. Features and advantages. Require translation. Portable. Easier to read, write and maintain as commands are similar to English. Allow access to module libraries. Use data types and data structures, selection statements and repetition/iteration constructs. Use logic operators and functions that are built into the language. Disadvantages . It ta...

What is an interrupt? An i nterrupt  is a signal from a device attached to a  computer  or from a program within the  computer  that requires the operating system to stop and figure out what to do next. Examples:  A  signal to stop Microsoft Word so that a PowerPoint presentation can gear up . When a key is pressed or when the mouse is moved. When communicating with the disk controller for reading and writing data to and from a disk. Steps an interrupt follows. Interrupt is raised Current CPU instruction is completed Contents of internal registers are stored in (pushed onto) the stack. The memory address of the ISR(Interrupt Service Routine) is found and transfer controlled. ISR is run Internal register contents are restored (popped) from the stack Original process continues from where it was stopped. What is a buffer? A  buffer  is a data area shared by hardware devices or program processes that  operate ...

1. An operating system ( OS ) is system software that manages computer hardware, software resources, and provides common services for computer programs.  Examples: Windows : Microsoft Windows has existed in one form or another since 1985 created by Bill Gates, and it remains the most popular operating system for home and office computers. Its latest versions, including Windows 10, are also used on some tablets, and the OS is used on some web and number-crunching server computers as well. Computers from a wide variety of manufacturers can use Windows. Apple iOS: Apple's iOS is one of the most popular smartphone operating systems by Steve Jobs, second only to Android. It runs on Apple hardware, including iPhones, iPad tablets and iPod Touch media players. Signature features of iOS include the App Store where users buy apps and download free software, an emphasis on security including strong encryption to limit what unauthorized users can extract from t...