Chapter 6 - Programming. This chapter presents the following content: Systematic decomposition; the three constructs: sequential, conditional, iterative; LC-3 control instructions to implement the three constructs; the character count example from chapter 5, revisited; debugging operations. | Chapter 6 Programming Problem solving Debugging Problem solving Start with systematic decomposition of problem “top-down” analysis stepwise refinement Algorithms must have properties of: finiteness completeness definiteness computability 6 - Structured programming Three control structures: Sequential This is the default Conditional Branching or decision-making Iteration Loops 6 - Implementing the control structures Sequential Conditional Iterative 6 - Stepwise refinement illustrated Character count algorithm: statement of problem & first level of refinement 6 - Stepwise refinement (cont.) 2nd & 3rd levels 6 - Stepwise refinement (cont.) Final level 6 - Debugging A debugging tool provides (at least) the ability to: Set values to registers & memory locations enter as hex, decimal or binary values Execute instructions one at a time, or in small groups Run will set the program running Step causes a fixed number of instructions to be executed (often used to “single-step” through part of a program) Stop execution when desired Breakpoints allow the user to set points at which execution will halt & wait for a new “Run” instruction Examine the contents of registers and memory locations at any point 6 - Debugging example A program to find the first 1 in a 16-bit word 6 - Debugging example (cont.) Oops! We have an infinite loop! Setting a breakpopint at location x3007 & repeatedly running the code shows that the loop does not trerminate because there is no 1 in the test case number 6 | Chapter 6 Programming Problem solving Debugging Problem solving Start with systematic decomposition of problem “top-down” analysis stepwise refinement Algorithms must have properties of: finiteness completeness definiteness computability 6 - Structured programming Three control structures: Sequential This is the default Conditional Branching or decision-making Iteration Loops 6 - Implementing the control structures Sequential Conditional Iterative 6 - Stepwise refinement illustrated Character count algorithm: statement of problem & first level of refinement 6 - Stepwise refinement (cont.) 2nd & 3rd levels 6 - Stepwise refinement (cont.) Final level 6 - Debugging A debugging tool provides (at least) the ability to: Set values to registers & memory locations enter as hex, decimal or binary values Execute instructions one at a time, or in small groups Run will set the program running Step causes a fixed number of instructions to be executed (often used to “single-step” through part of a program) Stop execution when desired Breakpoints allow the user to set points at which execution will halt & wait for a new “Run” instruction Examine the contents of registers and memory locations at any point 6 - Debugging example A program to find the first 1 in a 16-bit word 6 - Debugging example (cont.) Oops! We have an infinite loop! Setting a breakpopint at location x3007 & repeatedly running the code shows that the loop does not trerminate because there is no 1 in the test case number 6 -
