LAB 4 Extending Signed and Unsigned Numbers

Transcription

1 LAB 4 Extending Signed and Unsigned Numbers Objective: Explain unsigned and signed numbers, zero extension and sign extension, and variable declarations. The 80x86 provides several instructions that will let you sign or zero extend a number, for instance, an 8-bit binary number extending to a 16-bit binary number, a 16-bit binary number extending to a 32-bit binary number, or a 8-bit binary number extending to a 32-bit binary number. 80x86 instructions for sign extension and zero extension: MOVSX - move with sign extension for a signed number MOVSXD move with sign extension for a double word signed number MOVZX - move with zero extension for a unsigned number Another group of instructions will sign extend the AL, AX, or EAX registers. These instructions are: CBW - convert the byte in the AL register to a word in the AX register. CWD - convert the word in the AX register to a double word in DX:AX registers CDQ - convert the double word in the EAX register to the quad word in EDX:EAX registers CWDE - convert the word in the AX register to a double word in EAX register CDQE - convert the double word in the EAX register to a quad word in RAX register Include in your lab experiment the following: 1) Type and explain Example 1 (extendingnum.cpp). Compile, Build, and Run the program. Example 1 illustrates to use of a. unsigned numbers: an 8-bit unsigned char, a 16-bit unsigned short, a 32-bit unsigned int b. signed numbers: an 8-bit signed char, a 16-bit signed short, a 32-bit signed int c. printf() formatting %x (or %X) in C programming to display an 8-bit hexadecimal number d. printf() formatting %u in C programming to display a unsigned number e. printf() formatting %d (or %i) in C programming to display a signed number f. std::hex in C++ programming to display a 16-bit hexadecimal number or a 32-bit hexadecimal number g. std::dec to display a 16 bit decimal number or a 32 bit decimal number 2) Explain each line of Example 1 (extendingnum.cpp) and describe the output of each in your lab report 3) Initializing hexadecimal value in extendingnumtemp.cpp. Convert the hexadecimal number to decimal number. Show both hexadecimal number and decimal number of the output by using printf or cout functions: 1

2 Initialize hexadecimal value to an 8 bit unsigned memory variable, display the value in hexadecimal format and decimal format. Initialize hexadecimal value to an 8 bit signed memory variable, display the value in hexadecimal format and decimal format. Initialize hexadecimal value to a 16 bit unsigned memory variable, display the value in hexadecimal format and decimal format. Initialize hexadecimal value to a 16 bit signed memory variable, display the value in hexadecimal format and decimal format. 4) Modify the Example 2 provided in extendingnumtemp.cpp, and write an in-line assembly program that performs zero extension for an unsigned number and sign extension for a signed number. a. An 8-bit unsigned number to a 16-bit unsigned number conversion Input an 8-bit unsigned number (for example, hexadecimal of FD), and convert this value to the identical value with 16-bit unsigned number. Show before and after values of the b. An 8-bit signed number to a 16-bit signed number conversion Input an 8-bit signed number (for example, hexadecimal of FD), and convert this value to the identical value with 16-bit signed number. Show before and after values of the converted hexadecimal information and decimal information c. An 8-bit unsigned number to a 32-bit unsigned number conversion Input an 8-bit unsigned number (for example, hexadecimal of FD), and convert this value to the identical value with 32-bit unsigned number. Show before and after values of the d. An 8-bit signed number to a 32-bit signed number conversion Input an 8-bit signed number (for example, hexadecimal of FD), and convert this value to the identical value with 32-bit signed number. Show before and after values of the converted hexadecimal information and decimal information e. A 16-bit unsigned number to a 32-bit unsigned number conversion Input a 16-bit unsigned number (for example, hexadecimal of FFFD), and convert this value to the identical value with 32-bit unsigned number. Show before and after values of the f. A 16-bit signed number to a 32-bit signed number conversion 2

3 Input a 16-bit signed number (for example, hexadecimal of FFFD), and convert this value to the identical value with 32-bit signed number. Show before and after values of the Example 1 /*********************************************************** File name: extendingnum.cpp Extending Signed and Unsigned Numbers Method: Embedding an in-line assembly language module in a C/C++ program A. Extending 16-bit unsigned number to a 32-bit unsigned number B. Extending 16-bit signed number to a 32-bit signed number conversion printf() is used to display information on the console std::cout is used to display the output on the console std::cin is used to input the information from the keyboard std::hex is used to display hexadecimal value std::dec is used todisplay decimal value system ("pause") is used to hold console *************************************************************/ #include <stdio.h> #include <iostream> using namespace std; int main() //more variables should be declared //unsigned char us8 = 0xfd; //signed char s8 = 0xfd; unsigned short int us16 = 0xfffd; signed short int s16 = 0xffffd; unsigned int us32; signed int s32 ; //A 16-bit unsigned number extending to a 32-bit unsigned number printf("a 16-bit unsigned number extending to a 32-bit unsigned number\n"); printf("unsigned hexadecimal value is 0x%x\n", us16); printf("its associated unsigned decimal value is %u\n", us16); MOV AX, us16; //unsigned number move to AX MOVZX EAX, AX; //zero extension MOV us32, EAX; //move to 32-bit unsigned number cout << "After zero extension,\n" <<"the identical hex value with 32-bit unsigned number is " <<hex << us32 <<'\n' <<"and its associated decimal is "<< dec<< us32 <<'\n'; //A 16-bit signed number extending to a 32-bit signed number printf("a 16-bit signed number extending to a 32-bit signed number\n"); 3

4 cout << "signed hexadecimal value is " << hex<< s16 <<endl; cout << "its associated signed decimal value is "<<dec << s16<<endl; MOV BX, s16; //unsigned number move to BX MOVSX EBX, BX; //sign extension MOV s32, EBX; //move to 32-bit signed number cout << "After sign extension,\n" <<"the identical hex value with 32-bit signed number is " <<hex << s32 <<'\n' <<"and its associated decimal is "<< dec<< s32 <<'\n'; system ("pause"); return 0; The output from extendingnum.cpp Example 2 (Template) /*********************************************************** File name: extendingnumtemp.cpp Extending Signed and Unsigned Numbers Method: Embedding an in-line assembly language module in a C/C++ program A. Extending 16-bit unsigned number to a 32-bit unsigned number B. Extending 16-bit signed number to a 32-bit signed number conversion printf() is used to display information on the console std::cout is used to display the output on the console std::cin is used to input the information from the keyboard std::hex is used to display hexadecimal value std::dec is used todisplay decimal value system ("pause") is used to hold console *************************************************************/ #include <stdio.h> #include <iostream> 4

5 using namespace std; int main() //more variables should be declared unsigned char us8 = 0xfd; signed char s8 = 0xfd; unsigned short int us16; signed short int s16; unsigned int us32; signed int s32 ; //A 8-bit unsigned number extending to a 16-bit unsigned number printf("an 8-bit unsigned number extending to a 16-bit unsigned number\n"); printf("unsigned hexadecimal value is 0x%x\n", us8); printf("its associated unsigned decimal value is %u\n", us8); //After zero extension, the identical unsigned 16-bit hexadecimal value //After zero extension, the identical unsigned 16-bit decimal value //A 8-bit signed number extending to a 16-bit signed number printf("an 8-bit signed number extending to a 16-bit signed number\n"); printf("signed hexadecimal value is 0x%x\n", s8); printf("its associated signed decimal value is %d\n", s8); //After sign extension, the identical signed 16-bit hexadecimal value //After sign extension, the identical signed 16-bit decimal value r //A 8-bit unsigned number extending to a 32-bit unsigned number printf("an 8-bit unsigned number extending to a 32-bit unsigned number\n"); printf("unsigned hexadecimal value is 0x%x\n", us8); printf("its associated unsigned decimal value is %u\n", us8); 5

6 //After zero extension, the identical unsigned 32-bit hexadecimal value //After zero extension, the identical unsigned 32-bit decimal value //A 8-bit signed number extending to a 32-bit signed number printf("an 8-bit signed number extending to a 32-bit signed number\n"); printf("signed hexadecimal value is 0x%x\n", s8); printf("its associated signed decimal value is %d\n", s8); //After sign extension, the identical signed 32-bit hexadecimal value //After sign extension, the identical signed 32-bit decimal value r system ("pause"); return 0; 6