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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 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 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 Assembler Machine Language Program 0000 1010 1100 0101 1001 1111 0110 1000 lw lw sw sw 1100 0101 1010 0000 $15, $16, $16, $15, 0110 1000 1111 1001 1010 0000 0101 1100 0($2) 4($2) 0($2) 4($2) 1111 1001 1000 0110 0101 1100 0000 1010 1000 0110 1001 1111 Machine Interpretation Control Signal Specification ALUOP[0:3] <= InstReg[9:11] & MASK Multi-level organization: summary 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