1. Theory Fundamentals
A section of Computer Science, 9608
Listing 10 of 304 questions
A digital camera takes a bitmap image. The image is 2000 pixels wide by 1000 pixels high with a colour depth of 24-bits. Calculate an estimate of the file size for the image. Give your answer in megabytes. Show your working. Working Answer MB A second image is taken, this time in black and white. It has the same number of pixels, but the file size is smaller. Explain why the file size is smaller. The digital camera allows a user to add text to an image. The text is encoded as ASCII values. The table shows the ASCII denary values for five characters. Character ASCII denary value a b c d e Give the 8-bit binary value for the ASCII character ‘b’. Complete the table by writing the ASCII denary value for the character ‘t’ and its hexadecimal equivalent. Character t ASCII denary value Hexadecimal value
9608_s20_qp_11
THEORY
2020
Paper 1, Variant 1
View
A train cannot move if any of the eight automatic train doors are open. The train door monitoring system, set out below, checks that all the doors are closed before the train can move. • If a monitoring system detects that a door is open, it sets a specific bit in address 500 to 1. • If the bit for door one is equal to 1, the binary value for hexadecimal FF is sent to address 501. The contents of address 501 are changed to make door 1’s light flash when the door is open. • If the bit for door two is equal to 1, the binary value for hexadecimal FF is sent to address 502. The contents of address 502 are changed to make door 2’s light flash when the door is open. This is repeated for each door from 3 to 8. • Each door sets its bit in address 500 to zero when the door closes, and the contents of the corresponding door address are set to zero. • The train manager can identify which door is open from the flashing light. The current contents of address 500 are: Door number Address 500 Complete the following table by writing the values stored in addresses 503 to 508. Use the contents of address 500 shown above. Note that addresses 501 and 502 are complete. Door 1 Door 2 Door 3 Door 4 Door 5 Door 6 Door 7 Door 8 The following table shows assembly language instructions for the processor controlling the train door monitoring system that has one general purpose register, the Accumulator (ACC). Instruction Explanation Label Op code Operand LDM &n Load the hexadecimal number n to ACC LDD Load the contents of the location at the given address to ACC STO Store the contents of ACC at the given address AND &n Bitwise AND the contents of ACC with the hexadecimal number n CMP &n Compare the contents of ACC with the hexadecimal number n JPE Following a compare instruction, jump to or if the compare was True : Labels an instruction WAIT Macro to wait one second before the next instruction is executed After rechecking the doors, address 500 now contains 10101010. Complete the table by writing the values of the Accumulator (ACC) and the contents of address 501 as these instructions are executed once to check door 1. Instruction ACC Label Op code Operand CHECK1: LDD AND &80 CMP &00 JPE DOOR1 LDM &FF DOOR1: STO WAIT LDM &00 STO WAIT JMP CHECK1 Write the assembly language instructions to check door 2. Instruction Label Op code Operand Explain how the check door routines show a flashing light or no light.
9608_s20_qp_31
THEORY
2020
Paper 3, Variant 1
View
A train cannot move if any of the eight automatic train doors are open. The train door monitoring system, set out below, checks that all the doors are closed before the train can move. • If a monitoring system detects that a door is open, it sets a specific bit in address 500 to 1. • If the bit for door one is equal to 1, the binary value for hexadecimal FF is sent to address 501. The contents of address 501 are changed to make door 1’s light flash when the door is open. • If the bit for door two is equal to 1, the binary value for hexadecimal FF is sent to address 502. The contents of address 502 are changed to make door 2’s light flash when the door is open. This is repeated for each door from 3 to 8. • Each door sets its bit in address 500 to zero when the door closes, and the contents of the corresponding door address are set to zero. • The train manager can identify which door is open from the flashing light. The current contents of address 500 are: Door number Address 500 Complete the following table by writing the values stored in addresses 503 to 508. Use the contents of address 500 shown above. Note that addresses 501 and 502 are complete. Door 1 Door 2 Door 3 Door 4 Door 5 Door 6 Door 7 Door 8 The following table shows assembly language instructions for the processor controlling the train door monitoring system that has one general purpose register, the Accumulator (ACC). Instruction Explanation Label Op code Operand LDM &n Load the hexadecimal number n to ACC LDD Load the contents of the location at the given address to ACC STO Store the contents of ACC at the given address AND &n Bitwise AND the contents of ACC with the hexadecimal number n CMP &n Compare the contents of ACC with the hexadecimal number n JPE Following a compare instruction, jump to or if the compare was True : Labels an instruction WAIT Macro to wait one second before the next instruction is executed After rechecking the doors, address 500 now contains 10101010. Complete the table by writing the values of the Accumulator (ACC) and the contents of address 501 as these instructions are executed once to check door 1. Instruction ACC Label Op code Operand CHECK1: LDD AND &80 CMP &00 JPE DOOR1 LDM &FF DOOR1: STO WAIT LDM &00 STO WAIT JMP CHECK1 Write the assembly language instructions to check door 2. Instruction Label Op code Operand Explain how the check door routines show a flashing light or no light.
9608_s20_qp_33
THEORY
2020
Paper 3, Variant 3
View
Four greenhouses are used to grow tomatoes. The temperature inside each greenhouse should be kept between 10 and 20 degrees Celsius inclusive. Each greenhouse has a temperature sensor. A computer system is programmed to control each greenhouse’s temperature by: • turning on the heater and closing the ventilation when the temperature falls below 10 degrees • turning off the heater and opening the ventilation when the temperature rises above 20 degrees. State the name given to the type of system described. Justify your answer to part . The computer system stores the temperature readings for the four sensors in two’s complement form and in four eight-bit memory locations with addresses 701 to 704. Greenhouse 1 Greenhouse 2 Greenhouse 3 Greenhouse 4 State the greenhouse numberwhere the temperature is out of range and give the valueof these temperaturein denary. The status of the heaters and the ventilation is shown at location 700. • A value of 1 means that the heater is on. • A value of 0 means that the heater is off. • A value of 1 means that the ventilation is open. • A value of 0 means that the ventilation is closed. The status of the heaters is shown in the most significant four bits; the status of the ventilation is shown in the least significant four bits. The pattern of bits at location 700 shows that the heater for greenhouse 3 is on and the ventilation for greenhouse 1 is open. Greenhouse number Heater Ventilation Show the pattern of bits when the heater is on for greenhouses 1 and 2 only and no ventilation is open. The table shows assembly language instructions for the greenhouse computer system that has one general purpose register, the accumulator (ACC). Instruction Explanation Label Op code Operand LDM &n Load the hexadecimal number n to ACC LDD Load the contents of the location at the given address to ACC STO Store the contents of ACC at the given address AND &n Bitwise AND operation of the contents of ACC with the hexadecimal number n LSL #n Bits in ACC are shifted denary number n places to the left. Zeros are introduced at the right hand end CMP &n Compare the contents of ACC with the hexadecimal number n JPE Following a compare instruction, jump to or if the compare was True : Labels an instruction If the bit for a greenhouse’s heater and the bit for the same greenhouse’s ventilation are both set to 1, a routine at label ERROR is executed. This routine has not been provided. These assembly language instructions check for an error in the greenhouse 1 system. LDD AND &88 CMP &88 JPE ERROR Explain the purpose of each instruction. Write the assembly language instructions to check for an error in the greenhouse 2 system.
9608_s21_qp_32
THEORY
2021
Paper 3, Variant 2
View
A touch screen has three squares where a selection can be made: T S U The x-coordinate of the centre of the three squares is held in three memory locations: Address Memory contents S 0000 1011 0100 T 0010 0101 0100 U 0100 0110 1100 Give the hexadecimal value of the memory contents for U. Convert the denary number 40 into binary. Bitmap graphics are used to represent squares S, T and U. These can be saved in a number of different image resolutions. Give the number of bits required to store each pixel for a black and white bitmap. Identify how many bits are required to store each pixel for a 256-colour bitmap. Explain your answer. Images can be compressed to reduce file size. Describe how lossless compression techniques work. Describe how lossy compression techniques work.
9608_w15_qp_12
THEORY
2015
Paper 1, Variant 2
View
Convert the denary number 46 to an 8-bit binary integer. Convert the denary integer – 46 to an 8-bit two’s complement form. Convert the denary number 46 into hexadecimal. Binary Coded Decimal (BCD) is another way of representing numbers. Describe how denary integers larger than 9 can be converted into BCD. Give an example in your answer. Describe how an 8-bit BCD representation can be converted into a denary integer. Give an example in your answer.
9608_w16_qp_11
THEORY
2016
Paper 1, Variant 1
View
Convert the denary number 46 to an 8-bit binary integer. Convert the denary integer – 46 to an 8-bit two’s complement form. Convert the denary number 46 into hexadecimal. Binary Coded Decimal (BCD) is another way of representing numbers. Describe how denary integers larger than 9 can be converted into BCD. Give an example in your answer. Describe how an 8-bit BCD representation can be converted into a denary integer. Give an example in your answer.
9608_w16_qp_13
THEORY
2016
Paper 1, Variant 3
View
Each of the following bytes represents an integer in two’s complement form. State the denary value. 0111 0111 Denary 1000 1000 Denary Express the following integer in two’s complement form. -17 State in denary, the range of integer values that it is possible to represent in two’s complement integers using a single byte. Lowest value Highest value Convert the following denary integer into Binary Coded Decimal (BCD). A 3-digit BCD representation has been incorrectly copied. It is shown as: State how you can recognise that this is not a valid BCD representation. Describe a practical application where BCD is used.
9608_w17_qp_11
THEORY
2017
Paper 1, Variant 1
View
Each of the following bytes represents an integer in two’s complement form. State the denary value. 0111 0111 Denary 1000 1000 Denary Express the following integer in two’s complement form. -17 State in denary, the range of integer values that it is possible to represent in two’s complement integers using a single byte. Lowest value Highest value Convert the following denary integer into Binary Coded Decimal (BCD). A 3-digit BCD representation has been incorrectly copied. It is shown as: State how you can recognise that this is not a valid BCD representation. Describe a practical application where BCD is used.
9608_w17_qp_13
THEORY
2017
Paper 1, Variant 3
View
Questions Discovered
304