K Hinds Page No. 1. Lecture 3 ASCII

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1 Page No. 1 ASCII Lecture 3 ASCII stands for American Standard Code for Information Interchange. Computers can only understand numbers, so an ASCII code is the numerical representation of a character such as 'a' or '@' or an action of some sort. ASCII was developed a long time ago and now the non-printing characters are rarely used for their original purpose. Below is the ASCII character table and this includes descriptions of the first 32 non-printing characters

2 Page No. 2 Hardware Specification of a Computer System CPU/Processor There are two main manufactures of microprocessors today. They are Intel and AMD. Though IBM was once a leader in this field, today they have diverted their interest into other areas of computing and wide scale CPU manufacturing is not directly one of those initiatives. Processor Speed Processors can be identified by how fast they are and by how many cores they contain. The speed of a processor is a fairly simple concept. Speed is counted in megahertz (MHz), which means millions of cycles per second and faster is better. Typical operating speeds today for personal computers range from 1GHz to 4 GHz. Multi-Core Processors A multi-core processor is a single computing component with two or more independent actual processing units (called "cores"), which are the units that read and execute program instructions. The instructions are ordinary CPU instructions such as add, move data, and branch, but the multiple cores can run multiple instructions at the same time, increasing overall speed for programs. Processors are made as duo core, quad core and recently as octal core. Processor Brand and Form Factor Processors also come in different shapes and physical sizes. Intel range of processors are only compatible with Intel motherboards and AMD processors are only compatible with AMD motherboards due primarily to their physical shape, but also to the supporting electronic composition of the motherboards. Processor Cache (Processor Memory) Most processors today need an Immediate Access Store (Primary Memory) located within or on the CPU for direct access to instructions at high access and response speeds. To facilitate this memory, processors carry Cache memory. L1 and L2 are levels of cache memory in a computer. If the computer processor can find the data it needs for its next operation in cache memory, it will save time compared to having to get it from random access memory. L1 is "level-1" cache memory, usually built onto the microprocessor chip itself. For example, the Intel MMX microprocessor comes with 32 thousand bytes of L1. L2 or L3 (that is, level-2 or level -3) cache memory is on a separate chip (possibly on an expansion card) that can be accessed more quickly than the larger "main" memory. A popular L2 cache memory size is 1,024 kilobytes (one megabyte). Processor Capacity (Word Size) Capacity refers to the number of bits that a CPU can process at one time. Processors with many different word sizes have existed though powers of two (8, 16, 32 and 64 bits) have predominated for many years. A processor's word size is often equal to the width of its external data bus. Today the 32 and 64 bit word sizes are the standard instruction sets for issuing a single instruction to a CPU.

3 Page No. 3 Hard Drive A hard disk drive (HDD), hard disk, hard drive or fixed disk is a data storage device used for storing and retrieving digital information using one or more rigid ("hard") rapidly rotating disks (platters) coated with magnetic material. The platters are paired with magnetic heads arranged on a moving actuator arm, which read and write data to the platter surfaces. Data is accessed in a random-access manner, meaning that individual blocks of data can be stored or retrieved in any order rather than sequentially. HDDs retain stored data even when powered off. Hard Disk Drives (HDD) come in many sizes, speed, connection interfaces and composition for personal computers today. HDD s can either be used internally or externally. Capacity HDD s are made in sizes within the Giga Byte range (GB). Typical HDD s begin at 25GB and go up to 2TB (Terra Byte). The size of HDD required for the computer is dependent on what the computer is to be used for. Speed HDD s are also rated based on their rotating speed. Usually counted in revolutions per minute (rpm). A typical HDD today rotates at 5000rpm or as fast as 7500rpm. The higher rpm s the faster the HDD is at receiving a request and returning a response. Unfortunately this will also mean that more heat is generated by the drive as it will also have to consume more power in order to gain the benefit of a faster speed.

4 Page No. 4 Computer Ports & Expansion Slots USB Universal Serial Bus Also known as IEEE 1394, USB is the most popular connection used to connect a computer to devices such as digital cameras, printers, scanners, and external hard drives. USB is a cross-platform technology that is supported by most of the major operating systems. On Windows, it can be used with Windows 98 and higher. USB is a hot-swappable technology, meaning that USB devices can be added and removed without having to restart the computer. USB is also plug and play. When you connect a USB device to your PC, Windows should detect the device and even install the drivers needed to use it. There are three versions of USB. USB 1.0, only supported speeds of up to 11 Mbps and was used mostly to connect keyboards and mice. USB 2.0, supports speeds of up to 480 Mbps. USB 3.0 is the third major version for interfacing computers and electronic devices up to 625 MB/s. In order to take advantage of the higher speeds of USB 2.0 and 3.0 you will need to have ports installed on your computer that are also USB 2.0 and 3.0. Fire wire FireWire is a method of transferring information between digital devices. Also known as IEEE 1394 like its USB variant, FireWire is fast -- the latest version achieves speeds up to 800 Mbps. FireWire is hot swappable, meaning that you can add and remove devices connected on its ports at any time. It also supports up to 63 devices on a single FireWire bus. Windows operating systems (98 and later) and Mac OS (8.6 and later) both support it. Expansion Slots Expansion slots are located on the motherboard and resemble the image to the left. These expansion slots are referred to as Peripheral Component Interconnect slots (PCI). These expansion slots allows the addition of additional hardware devices to the computer.

5 Page No. 5 Ports A computer facilitates the connection of other devices to it using ports. The below images show some commonly used ports on a computer:

6 Page No. 6 Application and System Programs Software Application programs are used to take user input and then perform a specific function directly for the user or, in some cases, for another application. Examples of application programs are Microsoft Office, Adobe reader, games, Chrome and Flash Player. System programs are used to control the hardware of the computer system and provide a platform for application programs to run on. Examples of system programs are operating systems (Windows 7, Windows Server 2012, Macintosh, Android and Linux) as well as Programmable Language Software and Data Backup. Operating System An Operating System (OS) is a program installed onto a computer to control both its hardware and software resources. The OS provides a platform for other programs to run and acts as the intermediary between the application software and the hardware interface. There are many different Operating systems available today such as Windows 7/8/10, Windows Server, Apache Server, Android and Apple OS for mobile devices and Linux OS. Translators Assembler An assembler translates assembly language into machine code. Assembly language consists of mnemonics for machine opcodes so assemblers perform a 1:1 translation from mnemonic to a direct instruction. For example: LDA #4 converts to Conversely, one instruction in a high level language will translate to one or more instructions at machine level. Advantages of using an Assembler Very fast in translating assembly language to machine code as 1 to 1 relationship Assembly code is often very efficient (and therefore fast) because it is a low level language Assembly code is fairly easy to understand due to the use of English-like mnemonics Disadvantages of using Assembler Assembly language is written for a certain instruction set and/or processor Assembly tends to be optimized for the hardware it's designed for, meaning it is often incompatible with different hardware Lots of assembly code is needed to do relatively simple tasks, and complex programs require lots of programming time Compiler A Compiler is a computer program that translates code written in a high level language to a lower level language, object/machine code. The most common reason for translating source code is to create an executable program (converting from a high level language into machine language). Advantages of using a compiler Source code is not included, therefore compiled code is more secure than interpreted code Tends to produce faster code than interpreting source code Produces an executable file, and therefore the program can be run without need of the source code

7 Page No. 7 Disadvantages of using a compiler Object code needs to be produced before a final executable file, this can be a slow process The source code must be 100% correct for the executable file to be produced Interpreter An interpreter program executes other programs directly, running through program code and executing it line-by-line. As it analyses every line, an interpreter is slower than running compiled code but it can take less time to interpret program code than to compile and then run it this is very useful when prototyping and testing code. Interpreters are written for multiple platforms, this means code written once can be run immediately on different systems without having to recompile for each. Examples of this include flash based web programs that will run on your PC, MAC, games console and Mobile phone. Advantages of using an Interpreter Easier to debug(check errors) than a compiler Easier to create multi-platform code, as each different platform would have an interpreter to run the same code Useful for prototyping software and testing basic program logic Disadvantages of using an Interpreter Source code is required for the program to be executed, and this source code can be read making it insecure Interpreters are generally slower than compiled programs due to the per-line translation method System Utilities System utilities (also called system tools) are the core software functions that allow you to conduct maintenance tasks on your computer. Disk Cleanup Disk Cleanup is a function that comes with all versions of Windows Operating Systems. Disk Cleanup allows for you to scan your entire hard drive to search for extra room by deleting any unnecessary files such as temporary files from the Internet and cookies that are downloaded when you visit webpages. Disk Defragmenter The main function of the Disk Defragmenter is to reassemble fragmented files. Whenever a file is modified in any way, the computer stores the file in broken pieces across the hard drive rather than putting the whole file in one spot. This can lead to system malfunction and poor performance because your computer must search for all the pieces of a specific file before it can display it. The Disk Defragmenter searches for all pieces of every file on your hard drive and reassembles the files into a specific location. This increases the speed at which files are displayed and results in less delays when opening files or programs. System Restore System Restore is a function that comes with Windows that allows you to return your computer to an earlier time in which you had not encountered an error. System Restore is great for fixing problems that a virus has caused after you use antivirus software to rid your computer of the malware. System Restore allows you to manually set Restore Points on a calendar and also automatically creates Restore Points on a regular basis as well as right before your computer goes through any major change such as installing a new program.

8 Page No. 8 Disk Compression and Archivers Disk compression is a type of function that allows for a program to search your hard drive and compress files, particularly old or unused files. This greatly improves your computer s functionality and performance because it does not have to keep track of so many files at once. It also serves to free up space, which is the main function of disk compression software. Archivers, another form of file compression software, allows for you to compress a file or folder and then decompress the file whenever you decide to. The most popular archiver to date is Winrar, which is named after Winzip but has no affiliation. Both Winrar and a plethora of disk compression programs are available on the Internet at no charge. Registry Cleaners Registry cleaners are programs that allow for you to scan your computer for any errors in the registry, which is a collection of the core computer files that are essential to performance and functionality, and repairs them if needed. Registry cleaners are widely available on the Internet and give you a significant upper hand when cleaning up the mess that a virus or other malware has left on your computer. Likewise, some otherwise safe programs can cause errors in the registry without intending to. Registry files can also be corrupted if the user unknowingly deletes or modifies a file in the registry. This usually occurs when an inexperienced user tries to fix their computer and inevitably causes more damage than before. File Splitters File splitters are programs that allow you to break a file into smaller pieces in order to store or send files. File splitters often come in handy because many online storage services, including attachments, limit you to a specific file size that can be transferred at one time even though files often exceed these limits. File splitters allow you to break the file into two or more pieces, send them simultaneously, and then piece them back together when you are ready to use the file again. Application Software Categories Application software is used to provide a particular function to users. To this effect, software can be categorized into general purpose, special purpose, integrated and custom written. General Purpose Software This software is made to cater to general needs of end users across differing backgrounds. For example, word processor programs (MS Word) come in a standard edition so that it can be used by end users to create a letter, novel, poster or even a website. Customized Software This software is based on generalized software but it goes a step further as it allows modules to be added or removed from it. These modules usually improve the functionality of the software and allows the software to be tailored to its environment. An example of tailored software is Windows Server (Network Operating System). Modules can be added or removed to increase performance depending on the size of the organization. Special Purpose Software This software was made to facilitate a particular task that general purpose software would be unable to perform. Special purpose software can be graphic programs that edit photos (Photoshop), accounting packages (QuickBooks) software and music emulator programs among others. Integrated Software This software is a collection of highly used features of other software programs that are rolled into one single user friendly program.

9 Page No. 9 Custom Written Software This is software made for a particular hardware platform or purpose. Custom software is used by manufacturers to control robots, manufacturing plants assembly lines or any other computerized task that is not in mainstream use today. Functions of an Operating System User Interface (UI) Management File Management I/O Management Security Device Management Memory Management Process Management The operating system controls every task your computer carries out and manages system resources There are different kinds of Operating Systems in use today, these include Windows, Linux and Macintosh Operating Systems. There are also different versions of these operating systems, e.g. Windows 8 and Windows 10, Macintosh Yosemite and Mountain Lion and Linux Ubuntu and Redhat. Operating systems can also be used with different user interfaces (UI): text user interfaces (TUI) and graphical user interfaces (GUI). Graphical user interfaces have many similarities in different operating systems: such as the start menu, desktop etc. An Operating System main responsibility is to manage the hardware and software resources of the computer. These resources include such things as the File Management, Memory Management, Security Device Management, Input/Output Management, User Interface and Process Management. It provides a stable, consistent way for applications to deal with the hardware without having to know all the details of the hardware. User Interface Management A user interface is the part of an operating system that the user uses to input and receive data. A text user interface (TUI, see the image to the left below) shows text, and its commands are usually written from the keyboard to the command line. The functions of graphical user interfaces (GUI, right-hand image below) are carried out by clicking and moving buttons, icons and menus with the mouse. If you look closer at the above images, you will see that they contain the same information: the directory list of one of the computer s directories, so note that you can often carry out the same tasks with a computer regardless of which kind of UI you are using. Text User Interface TUI In Windows 7, you can access a command prompt by following this procedure: open the Start menu and type cmd in its search field. Then press Enter on the keyboard to launch the command prompt in a separate window. With the command prompt, you have to type your commands from the keyboard.

10 Page No. 10 Graphical user interface (GUI) Most operating systems have a graphical user interface instead of an input text screen. The GUI is used to manage graphical objects (such as icons and images) with the help of a mouse or touch sensitive screen. File Management File management describes the methods for naming, storing and handling files by using appropriate file and folder naming strategies. The data that we work with on computers is kept in a hierarchical file system in which directories have files and subdirectories beneath them.