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

Level 6: The User Level 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 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 Level 4: Assembly Language Level o Acts upon assembly language produced from Level 5, as well as instructions programmed directly at this level. Level 3: System Software 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 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 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 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. The Computer Level Hierarchy

Levels of Representation High Level Language Program Assembly Language Program Machine Language Program Control Signal Specification Compiler Assembler Machine Interpretation temp = v[k]; v[k] = v[k+1]; v[k+1] = temp; lw$15,0($2) lw$15,0($2) lw$16,4($2) lw$16,4($2) sw$16,0($2) sw$16,0($2) sw$15,4($2) sw$15,4($2) ALUOP[0:3] <= InstReg[9:11] & MASK

Computers are designed as a series of levels Computers are designed as a series of levels Each level represent a different abstraction (hence a different language) 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 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 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. 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 Choosing data types and operations for each level is a fundamental part of computer architecture design Multi-level organization: summary