CSCI 235 — Review

The homeworks

The decoding assignment

This will not be on the upcoming exams.

	.file	"testit.c"
	.text
	.globl	un_c
	.type	un_c, @function
un_c:
.LFB0:
	.cfi_startproc
	movl	$0, %eax
	jmp	.L2
.L3:
	movslq	%eax, %rdx
	addl	%eax, (%rdi,%rdx,4)
	addl	$1, %eax
.L2:
	cmpl	%esi, %eax
	jl	.L3
	rep ret
	.cfi_endproc
.LFE0:
	.size	un_c, .-un_c
	.ident	"GCC: (Ubuntu 4.8.4-2ubuntu1~14.04.3) 4.8.4"
	.section	.note.GNU-stack,"",@progbits

It’s a function which ends at the rep ret.
A good picture of register usage for calls is CMU notes p 25.
- %rdi — argument 1
- %rsi (aka %esi) — argument 2
- %rdx must be a temporary
- %eax is a temporary
addl %eax, (%rdi,%rdx,4)
- The ultimate CISC instruction: See CMU notes p 36
- Adding %eax to element %rdx of an integer array located at %rdi
- (unsigned long)(void *)&X[i] is (unsigned long)(void *)X + (sizeof X[0])*i. See Subtask Five of the pre-assembly lab.
- Before C, it was X(5) not X[5] for array index

The C program — version 2

Start with homework version 1 solution.

Add something like this.

  // This section is for Part 2 of the assignment (HW7)
  char name[51] ;
  int hour ;
  int minute ;

  while(fscanf(fileIn, "%50s %d:%d", name, &hour, &minute) == 3) {
    fprintf(fileOut, "%-50s %02d:%02d \n", name, hour, minute) ;
  }
  fclose(fileIn);
  fclose(fileOut);
  return 0 ;

Expected access time

Be sure to complete the expected time homework before the exams. ECON 120 students call it “expected return”.

Some things you just have to know

C logical expressions — differences with Java
- false is zero
- true is an non-zero integer
C bitwise expressions — just like the Java bitwise expressions
Pointers
- The * and & operators.
- &V[i] versus V+i
Standard C I/O
- C/C++ printf and C/C++ scanf
- relation to Java format
int main(int argc, char *argv[])
binary arithmetic
- know the powers of 2 up to 1024
- know what computer geeks mean by 64k, 128M and 16G
Understand the mechanical aspects of combinational digital logic
- Boolean expressions, truth tables, combinational circuits

Getting ready for the prefinal and final

Review the exams!