Notes, summaries, assignments, exams, and problems for Computers

Telephone Means and Equipment

Fixed individual devices (copper networks have been replaced by optical fiber networks)

Private branch exchanges (PBX): it connects calls between two destinations or ends

Function: call transfers among extensions, caller ID…

Types: IP PBXs call centers, they manage just phone calls contact centres, they not only manage phone calls but emails, SMS, online messages, faxes, etc.

Mobile devices: PDA, Smartphone

Services: Internet, e-mail, videoconference, digital camera, audio an Video quality player, an agenda, GPS, own, Operating system

Additional services offered by the telephone equipment

Common features

A.Fixed telephony: -Notice of charge(aviso de cargo) you receive info on the cost of a call Call forwarding(desvio

Binary Operations and Number Systems

Bitwise Shift Operations

Left Shift

The left shift operator (<<) shifts bits to the left, filling the vacated positions on the right with zeros. This is equivalent to multiplying the number by powers of two.

Right Shift

The right shift operator (>>) shifts bits to the right. There are two types:

• Logical Right Shift: Fills the vacated positions on the left with zeros.
• Arithmetic Right Shift: Fills the vacated positions on the left with the most significant bit (sign bit) of the original number, preserving the sign for signed integers.

Decimal to Binary Conversion

To convert a decimal number to binary, repeatedly divide the decimal number by 2. Record the remainder (which will be either 0 or 1) from right... Continue reading "Essential Computer Science: Binary, OS Kernel, Von Neumann, Assembly" »

Framing bit stuffing:

Framing in Computer Network. Data link layer is responsible for something called Bit Stuffing in Computer Network. It is the division of stream of bits from network layer into manageable units (called frames). Frames could be of fixed size or variable size. Bit stuffing is the insertion of non-information bits into data.

framing: A frame is a digital data transmission unit in computer networking and telecommunication.

Bit Stuffing: Bit stuffing is the process of inserting non-information bits into data to break up bit patterns to affect the transmission of the network.

Byte Stuffing: It is a process that transforms a sequence of data bytes that may contain illegal or reserved values.

Memory Management Problems and Solutions

Deadlock Scenario

A system has four processes and five allocable resources. The current allocation and maximum needs are as follows:

What is the smallest value of x for which this is a safe state?

The needs matrix is as follows:

• 0 1 0 0 1
• 0 2 1 0 0
• 1 0 3 0 0
• 0 0 1 1 1

If x is 0, we have a deadlock immediately. If x is 1, process D can run to completion. When D is finished, the available vector is 1 1 2 2 1. Now, A has ‘10211’ and ‘11221’ is available which together satisfies maximum need. So, A is finished and now ‘2 1 4 3 2’ is available, which can satisfy C. Once C is done, the available resources are 3 2 4 4 2, which can help B finish. So, x =1 will do.

Memory Compaction

A swapping system eliminates... Continue reading "Memory Management: Algorithms and Techniques" »

5. A machine has a 32-bit address space and an 8-KB page. The page table is entirely in hardware, with one 32-bit word per entry. When a process starts, the page table is copied to the hardware from memory, at one word every 100 nsec. Lf each process runs for 100 msec (including the time to load the page table), what fraction of the CPU time is devoted to loading the page tables?

The page table contains 232 /213 entries, which is 524,288.  Loading the page table takes 52 msec. If a process gets 100 msec, this consists of 52 msec for loading the page table and 48 msec for running. Thus 52% of the time is spent loading page tables.

6. Suppose that a machine has 48-bit virtual addresses and 32-bit physical addresses. If pages are 4 KB, how many... Continue reading "Understanding Paging and Virtual Memory in Computer Architecture" »

Traffic Server Client Request and Response API Functions

This document describes the Traffic Server API functions related to client requests and responses.

Client Request Functions

Loop Invariant:

Big-Theta, Big-Oh, Big-Omega

The application of several binary codes in microprocessor technique

Nbà + integer arithmetic, table/matrix indexing, event counting., C2à integer arithmetic, exponents in floating point notation.,Bcdà Faults:not effetive use of binary Word, absence of sign., Grayà code disksor bars to control position of moving elements., AScià Communication(text), service of: mosaic display, printers, autonomous keyboards.

Neuman:

It has a single storage system, Processor needs two clocks cycles. Dont use pipeline, Only one bus is used for both data transfers, older

Harvards:

It has two separated memories, 1 cycle if appropiate pipeling strategies, It has separate data and instruction busses, modern

Enumerate the phases of processor instruction execution.

Instruction... Continue reading "Microprocessor Techniques: Binary Codes and Instruction Execution" »

FIR Filters

A Finite Impulse Response (FIR) filter is characterized by its finite-duration impulse response, settling to zero in a finite time. Unlike Infinite Impulse Response (IIR) filters, which can have internal feedback and respond indefinitely, an Nth-order discrete-time FIR filter's impulse response lasts precisely N+1 samples. FIR filters are predominantly implemented in software and can be continuous-time analog or digital and discrete-time.

Transfer Function of FIR Filter

Frequency Response

IIR Filters

An Infinite Impulse Response (IIR) filter is a recursive filter where the output is calculated using current and previous inputs and outputs. This feedback mechanism within the filter structure is a defining characteristic. IIR filter design... Continue reading "FIR vs. IIR Filters: Advantages, Disadvantages, & Structures" »

What is a Basic Block?

A basic block is a sequence of instructions with no embedded branches (except at the end) and no branch targets (except at the beginning). A compiler identifies basic blocks for optimization. An advanced processor can accelerate the execution of basic blocks.

Six Steps Involved in Procedure Calling

1. Place parameters in registers.
2. Transfer control to the procedure.
3. Acquire storage resources.
4. Perform the desired operation.
5. Place the result in a register for the caller.
6. Return to the point of origin.

Register Saving Responsibilities

Between the caller and callee, the responsibility for saving registers is as follows:

• Temporary registers ($t*): Can be overwritten by the callee.
• Saved temporary registers ($s*): Saved and restored by the