In NASM(Assembly Language), how would you convert a character from uppercase to lower case

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In NASM(Assembly Language), how would you convert a character from uppercase to lower case Segment .data;user input prompt prompt: db "Enter an uppercase letter: " lenPrompt: equ $-prompt;output display message and variables uppercase: db 0xff message: db " was entered, in lowercase it is: " lowercase: db 0xff newLine2: db 0x0d, 0x0a; carriage return/line feed lenOutput: equ $-uppercase segment .code global _start: _start:;display prompt mov edx, lenPrompt; provide prompt length mov ecx, prompt; provide prompt to display mov ebx, 1;file descriptor: stdout mov eax, 4; system call #: sysjwrite int 0x80;call operating system;get character mov eax, 3; system call #: sys_read mov ebx, 1;file descriptor: stdin mov ecx, uppercase;where to store the user input mov edx, 1; number of bytes to read int 0x80;call operating system; convert character to uppercase;put uppercase variable value into register A low byte;add hex 20 to register A low byte value;put register A low byte into lowercase variable;display the output message mov edx, lenOutput; provide Output message length mov ecx, uppercase; reference data to display mov ebx, 1;file descriptor: stdout mov eax, 4; system call #: sys_write int 0x80;call operating system;exit program mov eax, 1 int 0x80