Download The Computer Level Hierarchy

Computer Architecture
And Organization
UNIT-II
Multilevel View Point Of
A Machine
Multilevel View Point Of A Machine
Actual Multilevel Computer
The Computer Level Hierarchy
The Computer Level Hierarchy
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Level 6: The User Level
o
Program execution and user interface level.
o
The level with which we are most familiar.
Level 5: High-Level Language Level
o
The level with which we interact when we
write programs in languages such as C,
Pascal, Lisp, and Java.
The Computer Level Hierarchy

Level 4: Assembly Language Level
o
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Acts upon assembly language produced
from Level 5, as well as instructions
programmed directly at this level.
Level 3: System Software Level
o Controls executing processes on the system.
o Protects system resources.
o Assembly language instructions often pass
through Level 3 without modification.
The Computer Level Hierarchy

Level 2: Machine Level
o
Also known as the Instruction Set
Architecture (ISA) Level.
o
Consists of instructions that are particular to
the architecture of the machine.
o
Programs written in machine language need
no compilers, interpreters, or assemblers.
The Computer Level Hierarchy

Level 1: Control Level
o A control unit decodes and executes
instructions and moves data through the
system.
o Control units can be microprogrammed or
hardwired.
o A microprogram is a program written in a
low-level language that is implemented by
the hardware.
o Hardwired control units consist of hardware
that directly executes machine instructions.
The Computer Level Hierarchy

Level 0: Digital Logic Level
o This level is where we find digital circuits
(the chips).
o Digital circuits consist of gates and wires.
o These components implement the
mathematical logic of all other levels.
Levels of Representation
temp = v[k];
High Level Language
Program
v[k] = v[k+1];
v[k+1] = temp;
Compiler

Assembly Language
Program
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Assembler
Machine Language
Program
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1100
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$15,
$16,
$16,
$15,
0110
1000
1111
1001
1010
0000
0101
1100
0($2)
4($2)
0($2)
4($2)
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Machine Interpretation
Control Signal
Specification
ALUOP[0:3] <= InstReg[9:11] & MASK
Multi-level organization: summary
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Computers are designed as a series of levels
Each level represent a different abstraction (hence a
different language)
The bottom level is the actual computer and its (real)
machine language (low-level language)
The top-level is for High-Level Languages
(C,C++,Java, Prolog) easier for the final user
The set of data types and operations of each level is
called an architecture.
Choosing data types and operations for each level is
a fundamental part of computer architecture design