Outcome 2 – Computer Software The Range of Software Available The Different Categories of Software System Software Programming Languages Applications Software

2 – System Software 2.1 -The Operating System Manages the hardware & communicates with the user. O/S is broken down into layers so updates can be written for specific layers. Some parts of O/S held in ROM chips, but most parts held on disk – can be corrupted. Bootstrap program runs on start-up and loads in the rest of the O/S from disk.

Operating System Layers Kernal I/O FMS MMS CLI

2 – System Software –Single-user Operating System The tasks of a single-user operating system is to manage all the resources of a computer system. The main resources are. –File management. Memory management. Command language interpreter. Input - Output System Process Management

2 – System Software Single-user Operating System -Command Language Interpreter The operating system takes user commands from the keyboard and mouse. Passes them to the operating system which; –Carries out the command. –If command cannot be understood an error is reported and a suitable message given back to the user.

2 – System Software Single-user Operating System -File management The operating system supervises the creation, deletion and updating of files on backing storage A directory keeps track of where files are stored. This is a hierarchical directory structure in which files are placed in folders (directories) and sub-directories

2 – System Software Single-user Operating System -Memory management The operating system decides where programs and data are to be placed in main memory It also keeps track of what stage a program is at and this applies equally to the operating system's own memory space. If corrupted it could cause the computer to crash

2 – System Software Single-user Operating System - Input-Output System Peripherals all work at different speeds The I/O system hides the differences and it makes them all appear to operate in a similar manner. The I/O system does all the actual data transfers and issues the appropriate control signals to the peripherals. Manufacturer usually supplies software (called a driver) for the user to install on their hard disk.

2 – System Software Single-user Operating System - Process Management O/S decides which tasks get to use the processor Processor management is often called the Kernel of the system It is the core function of the OS 11 File management

2 – System Software Network Operating System All Stations should have the same O/S to use the network system and to share messages on the network system. Multi-User Access – Operating System must provide a “logging-on” procedure with passwords for security.The user ID controls what the user has access to on the network. File Attributes – A user usually has read/write (r/w) access to their own files, read-only access to shared files.

2 – System Software Network Operating System File and Print Services – different users have different levels of access. Data Sharing and Integrity –. Only one user can edit a shared file at any one time (locking-out system).

2 – System Software 2.2 Utility Programs Utility programs aid the maintenance of the computer or make the user’s life easier. Includes disk formatter, disk tools and defragmentation tools. –Files are saved wherever the system can find space in consecutive sectors. As files are added and deleted spaces become available and are all over the filing system. A de-fragger moves files around to create a contiguous system with no empty sectors.

2 – System Software 2.3 Translators A Translator turns a program written in a high- level language into machine code. The high-level language is the source code and the machine code is the object code. Compilers – translate the source code in one go and produces executable machine code. Interpreters – Translate and execute a program line by line. Interpreted programs run much slower than compiled. Interpreter is simpler to learn and use.

4 – Application Software 4.1 Types of Applications You need to be aware of applications which handle:- –Text (word processor, web browser) –Number (spreadsheet, accounts package) –Data (database, world wide web) –Communications ( , file transfer) –Graphics (painting, drawing, CAD) –Multimedia (sound, video) –Integrated Packages (Works v Office)

4 – Application Software 4.2 Features and Requirements All application packages have features which distinguish them e.g. –Database – search and sort data, print reports. –Multimedia – allows user to create presentations using sound and video. Application packages have minimum hardware requirements. –Memory – Minimum RAM used is specified. –Hard Disk – Minimum disk space for installation and running usually specified. –Processor and operating system. –Any specific peripherals.

4 – Application Software 4.3 Standards Each application package saves files in its own way. Standards set ways of saving data so other packages can read the data. –SYLK, standard for spreadsheets –RTF, standard for text –CSV, comma separated variable for database –JPEG, GIF, TIFF, for graphics