1. Computing and the Web Hardware and Software: Putting It Together

2. Overview • Key Concepts Review • The ROBOT Computer • Software Applications: Using Spreadsheets

3. Key Concepts Review • Character • Numeric • Graphical • Audio • Instructional • All computers have the same basic hardware components • Programming languages allow humans to instruct computers to accomplish tasks • Computers come in all different shapes and sizes • Information comes from variety of different sources and must be reduced to a common form

4. Key Concepts Review • Computers can’t manipulate data unless instructed to do so • All data to be manipulated in the computer must be in binary • Computer instructions are performed sequentially in the order presented • Every instruction in a program must have one and only one meaning • Computer instructions are divided into two segments: opcode and operand • Every computer language has some instructions that contain no operand • Programs written in any language can be converted into binary • Once a program is in binary, the computer can use it directly (machine code)

5. A Conceptual Computer • The ROBOT Computer • Domain: a room surrounded with walls which may or may not contain doors; the floor is composed of squares like a chess board; there are no obstructions in the room; the dimensions of the room are unknown • Movement: the Root always occupies one and only one square; if the Robot takes a step it stops in the next consecutive square it is facing; if the Robot turns it remains in the same square; the Robot’s arm (when extended) will occupy the square directly in front of the Robot; the Robot’s movements are controlled by a program • Language: the Robot programming language has only eight instructions; all but one instruction has a physical response from the Robot; all but one instruction have no operand

6. The Robot Instruction Set • 000 Step move forward one square • 001 Turn turn 90 degrees to the right • 010 Raise raise the Robot’s arm if possible • 011 Lower lower the arm if it was raised • 100 Sense [we aren’t going to use this] • 101 Goto change order of instruction execution • 110 Light turn off the Robot’s light • 111 Stop the Robot turns off its power

7. The Robot Instruction Set • Notes on usage: Instructions are executed sequentially from the Robot’s memory, unless a GOTO instruction changes the order of execution If the Robot attempts to raise its arm and cannot (due to an obstruction), its light will turn on and instruction execution will be ignored. If the Robot’s light is on, the only instruction it will not ignore is the LIGHT instruction, which will turn off the light and resume normal instruction execution.

8. The Robot Operation • The Robot can only do what it is instructed to do • The Robot has a memory into which programs are loaded • There are only 32 memory locations 0 – 31 • The Robot instructions must be specified in binary • The Robot will fetch instructions sequentially • When the Robot decodes an instruction it will know what to do based on the opcode • When the Robot executes an instruction there will be an observable action.

9. A Robot Program • What would a program look like to make the Robot walk to the wall and stop? Step Step Step Step Stop • Will this program get the Robot to the wall and make it stop? • Assume the Robot is positioned as shown and facing the bottom

10. A Robot Program • Will the program work if the Robot is positioned as in Fig 1? Why or why not? • Will the program work if the Robot is positioned as in Fig 2? Why or why not? • What needs to happen to the program so that it will work no matter where the Robot is placed in the room? • How can we make the Robot “aware” of its surroundings? Fig 1 Fig 2

11. A Robot Program • We need to use the Robot’s arm to check out the square that is in front of it 00000 Raise 00001 Lower 00010 Step 00011 Goto 00000 00100 Light 00101 . . . . The above sequence creates a “loop” back to location 00000 from location 00011. What will make the loop stop?

12. A Robot Challenge • Have the Robot find a corner and stop 00000 Raise 00001 Lower 00010 Step Walk to 1st wall 00011 Goto 00000 00100 Light 00101 Turn Head towards second wall 00110 Raise 00111 Lower 01000 Step Walk to 2nd wall 01001 Goto 00110 01010 Light 01011 Stop Stop