1. Copyright Arshi Khan1 System Programming Instructor Arshi Khan

2. Copyright Arshi Khan 2 Course contents System programming overview Application Vs System Programming System Software Operating System Device drivers OS calls Windows system programming for Intel386 Architecture Virtual Machine Virtual Device Driver Module Management

3. Copyright Arshi Khan 3 Computer Software consisting of programs, enables a computer to perform specific tasks, as opposed to its physical components (hardware) which can only do the tasks they are mechanically designed for. application software which perform productive tasks for users, system software which interface with hardware to run the necessary services for user-interfaces and applications, and middleware which controls and co-ordinates distributed systems.

4. Copyright Arshi Khan 4 Cont.. computer systems divide software systems into three major classes: system software. programming software. application software.

5. Copyright Arshi Khan 5 Computer Programming process of writing, testing, and maintaining the source code of computer programs. The source code is written in a programming language. This code may be a modification of existing source or something completely new. The process of writing source code requires expertise in many different subjects, including knowledge of the application domain, specialized algorithms, and formal logic.

6. Copyright Arshi Khan 6 Foundation of System Programming

7. Copyright Arshi Khan 7 What is System Programming? is the activity of programming system software. produce software which provides services to the computer hardware (e.g. disk defragmenter). requires a greater degree of hardware awareness. Implementing certain parts in operating system and networking requires systems programming  (for example implementing Paging (Virtual Memory) or a device driver for an operating system). The primary distinctive characteristic of systems programming when compared to application programming is that systems programming requires a greater degree of hardware awareness.

8. Copyright Arshi Khan 8 More specifically: the programmer will make assumptions about the hardware and other properties of the system that the program runs on, and will often exploit those properties. usually a low-level programming language or programming language dialect is used that:  can operate in resource-constrained environments  is very efficient and has little runtime overhead  has a small runtime library, or none at all  allows for direct and "raw" control over memory access and control flow  lets the programmer write parts of the program directly in assembly language debugging can be difficult if it is not possible to run the program in a debugger due to resource constraints. Running the program in a simulated environment can be used to reduce this problem.

9. Copyright Arshi Khan 9 Application Programming Computer programming (often simply programming) is the craft of implementing one or more interrelated abstract algorithms using a particular programming language to produce a concrete computer program. Programming has elements of art, science, mathematics, and engineering. is the process of writing, testing, and maintaining the source code of computer programs. The source code is written in a programming language. writing source code requires expertise in many different subjects, including knowledge of the application domain, specialized algorithms, and formal logic.

10. Copyright Arshi Khan 10 Memory CPU Disk Card read/punch Printer Teletype General hardware organization of a computer system

11. Copyright Arshi Khan 11 Programming system components Assemblers Loaders Subroutines Relocating Macros Compilers Formal Systems

12. Copyright Arshi Khan 12 Evolution of Operating System

13. Copyright Arshi Khan 13 Operating System

14. Copyright Arshi Khan 14 Operating System software that manages the sharing of the resources of a computer. An operating system processes raw system and user input and responds by allocating and managing tasks and internal system resources as a service to users and programs of the system. An operating system performs basic tasks such as controlling and allocating memory, prioritizing system requests, controlling input and output devices, facilitating networking and managing file systems. Most operating systems come with an application that provides an interface to the OS managed resources. Operating Systems themselves have no user interfaces. The operating system forms a platform for other system software and for application software.

15. Copyright Arshi Khan 15 Disk Drivers Device driver is a specific type of computer software developed to allow interaction with hardware devices. Typically this constitutes an interface for communicating with the device, through the specific computer bus or communications subsystem that the hardware is connected to, providing commands to and/or receiving data from the device, and on the other end, the requisite interfaces to the operating system and software applications. It is a specialized hardware-dependent computer program which is also operating system specific that enables another program, typically an operating system or applications software package or computer program running under the operating system kernel, to interact transparently with a hardware device, and usually provides the requisite interrupt handling necessary for any necessary asynchronous time- dependent hardware interfacing needs.

16. Copyright Arshi Khan 16 System calls

17. Copyright Arshi Khan 17 Operating System Calls (OS Calls) OS calls/system call is the mechanism used by an application program to request service from the operating system. System calls often use a special CPU instruction which causes the processor to transfer control to more privileged code, as previously specified by the more privileged code. When the system call is invoked, the program which invoked it is interrupted, and information needed to continue its execution later is saved. The processor then begins executing the higher privileged code, which, by examining processor state set by the less privileged code and/or its stack, determines what is being requested. When it is finished, it returns to the program, restoring the saved state, and the program continues executing.

18. Copyright Arshi Khan 18 There are dozens of system calls supported any Linux or UNIX kernel. Some common examples include: file I/O: process control: memory management: time management: interprocess communication (IPC):