Convert 1011 1100 to a decimal number, assuming binary representation.
(b) Convert 1011 1100 to a decimal number, assuming two¡¯s complement representation.
(c) Translate the following Sigma16 assembly language to a single line statement in high level language, assuming that y, i are integer variables and x is an array. The data statements for the variables are omitted for simplicity. Just identify the calculation performed and present it in a single statement.
load R1,i[R0] load R2,x[R1] lea R3,35[R0] div R4,R2,R3 store R4,y[R0]
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(d) Give a detailed account of the sequence of steps performed by the processor as it executes the instruction: store R3,z[R4]
(e) Computer architectures today are mostly 64-bit: give two potential benefits.
(f) There is an array named x that contains n integers, where n is an integer variable in memory. Write a Sigma16 assembly language program that creates another array y of length n which contains all the elements of array x but changes them to positive (take care to handle negative numbers and store as positive). The program must work correctly for any n and initial array of elements. You may assume that the variables have been declared but not initialised. Your program should exit cleanly.
Define the behaviour of a demultiplexer (the demux1 circuit), given the control input c and the data input d. Give a circuit that implements a demultiplexer using logic gates.
(b) Explain what the levels of abstraction of a computer system are. Include a diagram representing them.
(c) Given the following assembly program: load R2,x[R0]
load R3,y[R0] add R1,R2,R3 store R1,y[R0] trap R0,R0,R0
Show the content of the memory using three columns for each memory location to indicate: 1) address (four hex values); 2) contents; 3) what the contents mean.
(d) Consider a doubly linked ordered list where p is a pointer to a node in the list (not the header) and each node is a record consisting of three words: an integer value, a pointer to the previous node in the list prev, and a pointer to the next node in the list next. Note that the value of the header node is 0, the last node in the list has nil in the next field (nil is represented by 0), and the value of each node is greater than the prev node but less than the next node. The following program deletes the node whose value is equal to the input variable x (assume that x ¡ 0 and there is a node that meets this condition). Translate the program to Sigma16 assembly language. You don¡¯t need to write out the low level language version, and you don¡¯t need to define the variables or the linked list.
; given p = pointer to list, x = value to delete
while (*p).value /= x do if (*p).value < x
p := (*p).next else
p := (*p).prev q := (*p).prev;
(q*).next := (*p).next;
(e) Identify three different causes of interrupts in a computer system and give an example for each case.
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