Crash Course Computer Science: Operating Systems

Introduction

• Lecture by Carrie Anne
• Overview of the evolution of computers and operating systems (OS)

Early Computers (1940s-1950s)

• Ran one program at a time, using punch cards.
• Manual process: Programmers wrote code, handed it to operators.
• Slow computers led to the need for self-operating systems.

Birth of Operating Systems

• OS as a program with special privileges on hardware.
• First introduced in the 1950s as computers became more affordable and powerful.
• Early OSes allowed batch processing of programs, reducing downtime.

Batch Processing

• Computers could automatically load and execute batches of programs.

Challenges for Programmers

• Programmers needed to interface with various hardware peripherals.
• Writing low-level code was time-consuming and complex.
• Operating Systems introduced device drivers to simplify this process.
  • Example: Function calls like "print highscore" handled by the OS.

Resource Management in OS

Multitasking

• Developed in the late 1950s with the Atlas supercomputer.
• Atlas Supervisor (1962) used scheduling to run multiple programs.
• Allowed programs to continue running while waiting for I/O operations.

Memory Management

• Programs allocated distinct memory blocks; each program had its own memory space.
• Virtual Memory allowed programs to assume memory starts at address 0.
• OS managed memory allocation, providing dynamic memory allocation.
• Memory Protection ensured one program couldn't overwrite another's memory.

Significant Developments by 1970s

• Institutions had access to computers with multiple users via terminals.
• Time-sharing systems developed to allocate resources among users.
• Multics (1969): Influential time-sharing OS, but overly complex.

Unix

• Developed by Dennis Ritchie and Ken Thompson after Multics.
• Separated OS into kernel (core functionality) and tools.
• Simplicity led to Unix's popularity and support for diverse hardware.

Personal Computers and Operating Systems in the 1980s

• Rise of personal/home computers led to simpler OS designs.
• MS-DOS (1981): Popular but lacked multitasking and memory protection.
• Early versions of Windows (1985) had similar limitations.

Modern Operating Systems

• Current OS: Mac OS X, Windows 10, Linux, iOS, Android.
• All support multitasking, virtual memory, and memory protection.
• Ability to run multiple applications simultaneously due to advancements in OS development.

Conclusion

• Importance of decades of research in OS for modern computing capabilities.