The Computer CPU – Jumps

Finally just to show you that everything you could possibly want can be easily included in this simple processor architecture consider how you might implement a “jump to xxxx” instruction. Normally the next instruction to be executed is in the next sequential memory location but a jump makes the instruction at xxxx the next one. How can this be achieved? Easy! Just make the PC register correspond to register address 00 (rather than general purpose...

The Computer CPU – Op-code

The op-code isn’t just any old number; it has a structure. In our example the first two bits of the op-code act as a mini address that selects which register the operation is going to use – 11  A register, 10  B register, 01  C register and 00  D register. The top two bits give the operation to be performed on the register that is selected – e.g. 10 = load the register, 11 =...

The Computer CPU – The Fetch cycle

As well as the PC register, a processor also has an instruction register which is used to store the current program instruction. A system clock generator provides pulses that synchronize what happens in the entire machine – it doesn’t have to be this way but non-clock synchronized machines are much more difficult to build and, by for the same reason, to describe! What happens is that the PC register contains the address of the next...

The Computer CPU – Principles Of Execution

The real complexity of any computer system resides in the processor, but do you know how it works? I mean how it really works? How does the code that you write turn into something that does something? When you know how, it’s not magic – just a matter of “fetch” and “execute”. So far we have looked at the overall workings of a computer and specifically the memory principle. Memories are devices that when given...

MS-DOS: Need to know Part 2

So to read a file you first find its name, MyLetter say, in the root directory. You then know the number of the first block that it uses to store data – block 05 say. You can now read block 05 and process the data it contains.

MS-DOS: Need to know Part 1

Now that Microsoft has open sourced MS-DOS it’s a good time to look at filing systems, blocks and the FAT and how they are used. Let’s explore the basics of a DOS – Disk Operating System. There is a big problem with disk drives. No, not the constant running out of space that we used to suffer from, but the deeper computer science and engineering problem of actually making them useful at all. We are...

The top 10 things to consider when buying a new laptop

When people ask us which laptop is best for their needs, the first thing we tell them is that there is no clear answer. There are too many different types of laptops, and different price categories to suit them. However, we do give people a checklist that they should consider before splurging on a new device. 1. Size: If portability is your main concern, then you need to consider a notebook that has a small-ish...

32-bit vs 64-bit

32-bit vs 64-bit, yes this one topic computer buyers always ask. A 32-bit computer is a computer that is normally averaged. Its main purpose of build is to cut down cost as swift as possible and not degrade too much necessary quality. This type of computers are usually intended for the computer User whose task is to perform normal work like open word processing software, checking emails, instant messaging, watching videos or movies and numerous...