3. Programming (1)

Question 1

What is a computer program?

Answer 1

A program is a sequence of instructions (‘code’) to be executed by a computer. It may be organised in different ways (procedures, objects) and written in different languages. The processor executes instructions one after the other unless there is an explicit ‘branch’, ‘jump’ or ‘goto’ instruction.

Question 2

How are pushbuttons (with internal pullup resistors and LEDs connected to the mC?

Answer 2

Pushbuttons with internal pullup resistors on pin 12, active low. LEDs on pin 13, active high. DRAW DIAGRAM.

Question 3

What is machine code?

Answer 3

By the time a program is stored (‘burned’) in the program memory of a mC, it is just binary data (1’s and 0’s). It has a particular meaning to the mC and is called machine called.

Question 4

What is assembly language?

Answer 4

This is just words that can be translated directly into machine code.

Question 5

Does a programmer ever use assembly language?

Answer 5

Sometimes for critical parts of a program

Question 6

How is assembly language translated into machine code?

Answer 6

using an assembler.

Question 7

What is better than an assembler?

Answer 7

A compiler , which does a more thorough job and translates for a higher level language, such as C.

Question 8

What can the processor do?

Answer 8

1. Arithmetic
2. Logical
3. Bit operations
4. Functions (subroutines)
5. move data
6. Control Flow
7. Misc.

Question 9

What arithmetic can the processor do?

Answer 9

Add, subtract, increment, decrement, divide, multiply; all of these can be floating point or integer

Question 10

What logical operations can the processor do?

Answer 10

and, inclusive-or, exclusive-or, complement, rotate (shift)

Question 11

What bit operations can the processor do?

Answer 11

set or clear individual bits in any memory location

Question 12

What can the processor do with functions (subroutines)?

Answer 12

call and return

Question 13

What can the processor do to move data?

Answer 13

move data from any memory location to another

Question 14

What can the processor do to control flow?

Answer 14

If, then, else construction, loops, call functions

Question 15

What are the misc things a processor can do?

Answer 15

sleep, set and service interrupts, clear WDT - these are usually accomplished by setting/ clearing data in specific registers, and C can be used for this.

Question 16

What is source code (in C)?

Answer 16

When we write a C program we create a text file which contains the C statements and is known as the source code. This is a human readable file, which the mC cannot interpret.

Question 17

How is the source code made readable to the mC?

Answer 17

The compiler turns it into binary code (machine code). This is generally stored in another file and then transferred to the mC.

Question 18

What are variables?

Answer 18

In programming, a variable is a value that can change, depending on conditions or on information passed to the program

Question 19

How many bytes to store a day of the week?

Answer 19

This only needs to go fro 1-7 and so a byte is sufficient.

Question 20

How many bytes to store a reading from an ADC?

Answer 20

these have 12 bit precision and are always positive. One byte is not enough, so two bytes are required.

Question 21

How many bytes for a floating point number?

Answer 21

4 bytes.

Question 22

What does the variable TYPE tell the compiler?

Answer 22

How much memory it takes up and how that memory should be interpreted (e.g unsigned integer or a float)

Question 23

what is int?

Answer 23

int - a 4 byte integer from -2147483648 to 2147483647

Question 24

what is unsigned int?

Answer 24

this goes from 0 to 4294967295

Question 25

what is char?

Answer 25

a single character e.g ‘a’ or ‘T’

Question 26

what is float?

Answer 26

a real number with 6-7 decimal digits of precision. The max value is 3.4E+38 and the smallest positive number is 1.2E-38

Question 27

What are constants?

Answer 27

values which do not change, like variables because has a type and refers to a particular memory location. The compiler checks that you dont accidently change its value once it has been set