Microcomputers Interview Questions & Answers

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No bugs in the first, smaller, version of the software (256 bytes of code blown into PROM by Nick Toop?s PROM blower). There were a couple of problems with the cassette interface software because I got the order of bits the wrong way round (from the CUTS? standard). But hey, it was only 512 bytes: you can?t make any mistakes in that even when you write it by hand, hand assemble it and hand enter it into the PROM blower! Besides, it could debug itself to a fair extent (given that it basically worked).

★ Connectivity
★ Cost-effective Resource Sharing
★ Support for common Services
★ Performance

★ Physical Layer
★ Data link Layer and
★ Network Layers

If the message is sent from a source to a single destination node, it is called Unicasting.

If the message is sent to some subset of other nodes, it is called Multicasting.

If the message is sent to all the m nodes in the network it is called Broadcasting.

Science of Cambridge used 8154s on its MK14 kit (National SC/MP based) and so they were available when we needed something for the 6502. They were fairly cheap and the extra RAM was a bonus, even though it meant converting from 6502 clock/write to the read strobe/write strobe that they used.

Packing them in boxes (upstairs at 4a Market Hill): the whole company would stand around tables (a production square) and put in the right components (me, Hermann, Hermann?s then fianc? Stephen, Chris). We all did pretty much anything: I ended up as Hermann?s secretary before we could afford one!

There used to be problems with answering the phone: one chap would ring up and say ?I have got an Acorn, it does not work? often enough for it to become a legend. We got very tired of kits ? the highlight being a guy who assembled his Atom with glue because he knew that heat (solder) would damage them ? so that coloured the BBC machine a lot.

User data:
Modifiable part of user space. May include program data, user stack area, and programs that may be modified.
User program:
The instructions to be executed.
System Stack:
Each process has one or more LIFO stacks associated with it. Used to store parameters and calling addresses for procedure and system calls.
Process control Block (PCB):
Info needed by the OS to control processes

Not exactly based on anything. Most of its heritage was from an automated cow feeder that I?d designed for a Harrogate company the previous summer (1977). Quite an advanced thing, really ? it had a (waterproof) number pad, big 7 segment LEDs, OS in non-volatile EEPROM, and the trademark 6502. Both were from my own designs for something for myself, and they came from the aether.

The most hair-raising thing was the cow-feeder?s programme. I didn?t own a PROM blower, so I had to write the whole thing by hand and send it off to a company who hand entered it into a machine and sent me back the PROM. That worked first time, too. Mind you, it was even smaller, being a boot loader that allowed the cow-feeder?s EEPROM to be initialised.

DDks are device driver kits, which are equivalent to SDKs for writing device drivers. Windows NT includes DDks.

FDM is an analog technique that can be applied when the bandwidth of a link is greater than the combined bandwidths of the signals to be transmitted.

I had designed something similar for myself, and was in the process of helping Hermann [Hauser] with his ideas for an ?electronic pocket book? (what we might nowadays call a PDA). In the course of showing that my designs for it would work, I showed him my schematics for my own machine and was challenged to build it. So I did? With my own white ceramic 6502, too. That was ?just? the equivalent of the CPU board of the System 1 with LEDs and keyboard (all on the same bit of Veroboard) ? the cassette interface was added later. I think Hermann was overly impressed when it worked first time!

Because it was there. Because it was new. Because a few of the other members of the Cambridge University Processor Group [CUPG] were going on about it being easier to interface to circuits. I guess I don?t really know precisely why I chose the 6502 ? maybe we just had an affinity!
It cost quite a lot back in 1977/78 when I bought mine ? which was a wonderful white ceramic part with gold (coloured?) legs and lid.

Increased speed and memory capacity of microprocessors together with the support fir virtual memory and Growth of client server computing.

Free memory is maintained in linked lists, each of equal sized blocks. Any such block is of size 2k. When some memory is required by a process, the block size of next higher order is chosen, and broken into two. Note that the two such pieces differ in address only in their kth bit. Such pieces are called buddies. When any used block is freed, the OS checks to see if its buddy is also free. If so, it is rejoined, and put into the original free-block linked-list.

Defining a useful channel involves both understanding the applications requirements and recognizing the limitations of the underlying technology. The gap between what applications expects and what the underlying technology can provide is called semantic gap.

In STDM, the multiplexer allocates exactly the same time slot to each device at all times, whether or not a device has anything to transmit.

★ Security/Encapsulation
★ Distributed database
★ Faster Problem solving
★ Security through redundancy
★ Collaborative Processing

Also called FIFO anomaly. Usually, on increasing the number of frames allocated to a process virtual memory, the process execution is faster, because fewer page faults occur. Sometimes, the reverse happens, i.e., the execution time increases even when more frames are allocated to the process. This is Belady's Anomaly. This is true for certain page reference patterns.

★ Network redirector/ Server
★ Cache manager.
★ File systems
★ Network driver
★ Device driver

The Transport layer links the network support layers and user support layers.

★ Performance:
It can be measured in many ways, including transmit time and response time. ★ Reliability:
It is measured by frequency of failure, the time it takes a link to recover from a failure, and the network's robustness.
★ Security:
Security issues includes protecting data from unauthorized access and virues.

TDM is a digital process that can be applied when the data rate capacity of the transmission medium is greater than the data rate required by the sending and receiving devices.

a) Frequency of failure
b) Recovery time of a network after a failure