[CA] Lecture #03

The Operating System (OS) Manages the Hardware

▶ Operating System

• Protect the hardware from misuse by runaway applications.
• Provide applications with simple and uniform mechanisms for manipulating complicated and often widly different low-level hardware devices.

 

Concurrency(동시성) and Parallelism

Uniprocessor System

: The concurrent execution is only simulated, by having a single computer rapidly switch among its execution processes.

 

Multiprocessor System

• Hyperthreading = Simultaneous multi-threading
  : Single CPU execute multiple flows of control.
  --> CPU와 Thread의 개수가 다르다.

▶ Multiprocessing

• It reduces the need to simulate concurrency when performing multiple tasks.
• It can run a single application program faster, but only if the program is expressed in terms of multiple threads that can effectively execute in parallel.

• TLP(Thread-Level Parallelism)
  : GPU

 

Instruction-Level Parallelism (ILP)

▶ Pipelining
: The actions requred to execute an instruction are partitioned into different steps and the processor hardware is organized as a series of stages, each performing one of these steps.

Pipelining

• Superscalar processors
  : Processors that can sustain execution rates faster than 1 instruction per cycle.

 

SIMD Parallelism

▶ SIMD (Single-Instruction, Multiple-Data)

• Many modern processors have special hardware that allows a single instruction to cause multiple operations to be performed in parallel.

SIMD Parallelism

 

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Number Representation

Information Is Bits + Context

• All information in a system is represented as a bunch of bits.
• The only thing that distinguishes different data object is the context in which we view them.

 

Unsigned Integers

Decimal  & Binary Number

 

Octal & Hexadecimal Number

 

Decimal --> Binary

 

Binary --> Octal, Hexadecimal

 

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Modern Computers

• 8 bits = 1 byte

 

Signed Number

• Unsigned number
• Signed number 
  - MSB = 0 --> +
  - MSB = 1 --> -

 

Other Number Representations

Fixed-Point Numbers

• Fixed-Point Number = integer + fractional parts

Fixed-Point Numbers

• Fixed-point numbers have a range that is limited by significant digits used to present the number.

 

Floating-Point Numbers

: Floating-point representation in which numbers are represented by a mantissa comprising the significant digits and an exponent of the radix R.

Floating-Point Numbers