Instruction interpreter: is a group of electrical circuits that perform the intent of instructions fetched from memory.

Location Counter: Also called Program Counter or Instruction Counter, denotes location of current instruction executed.

Instruction Register: Stores copy of the current instruction.

Working Registers: Memory Devices that serve as a scratch pad for instruction interpreter.

General Registers: Used by the programmer as storage location for special functions.

Memory Address Register: Contains address of memory location where to write or read something.

Memory Buffer Register: Contains the contents of address specified by MAR, before writing or after reading from it.

Memory Controller: Is hardware that transfers data between MBR and core memory location.

I/O Channels: These interpret special instructions for input or output of the information from the memory.

Specific Details may vary from computer to computer, discussed one is the conventional machine structure.

For Programming at machine level, following questions must be answered:

1.Memory: What is the basic unit, size and addressing scheme of memory?

2.Registers: How Many Registers are there? What are their size, function and interrelationship?

3.Data: What types of the data can be handled? How is this data stored?

4.Instructions: What are the classes of instructions on the machine? What are their formats? How are they stored?

5.Special Features: What is the interrupt structure of the machine? What type of protection mechanism is available?

Units: Basic memory units is byte i.e. each addressable location in memory can contain 8 bits of information. To operate on contiguous locations Halfword, word or doubleword are used.

Size: about 224 bytes. Addressing Scheme:Address=value of an offset+contents

of a base register+contents of an index register;

16 general purpose registers of 32 bits each

4 floating point registers, 64 bits each. A 64 bit Program Status Word that

holds value of location counter, protection information and interrupt status.

e.g. A 1,901(2,15)

Advantages of Base Register Addressing: Convenient Relocation. Efficient Addressing Mechanism.

Disadvantage: Overhead associated with formation of

addresses. A 12 bit offset can not move more than

4095 location away from base register, without changing contents of base register and using and index register.

Groups of bits are interpreted by a 360 processor in several ways.

All data and instructions are stored as a sequence of binary ones and zeros.

For convenience binary numbers are stored as hexadecimals.

The prefixes X and B indicate mode of representation.

Fixed point numbers can be stored as either halfword or fullword.

A 360 allows to store numbers in binary formats e.g. 12 can be written in one byte where 4 bytes show 1(0001) and rest 4 bytes 2(0010)

The 360 has arithmetic, logical, control or special interrupt instructions.

There are types of instructions differ basically in the types of the operands they use. Register Operands refer to data stored in

one of the 16 general registers. Storage operands refer to data stored in

core memory. The length of data depends upon data type.

Immediate Operands are single byte of data and are stored as part of the instruction.