However, 32-bit PCs are being replaced with 64-bit ones, and the underlying assembly code has changed. The second operand could be either in register/memory or an immediate (constant) value. Since most of the instructions we'll go over are for data operations, I've grabbed the data-processing instruction out of the ARMV7 manual. The full x86 instruction set is large and complex (Intel's x86 instruction set manuals comprise over 2900 pages), and we do not cover it all in this guide. If the bits from the operands are same (both 0 or both 1), the resultant bit is cleared to 0.The TEST instruction works same as the AND operation, but unlike AND instruction, it does not change the first operand. The OR instruction is used for supporting logical expression by performing bitwise OR operation. The high-order 32 bits are in EDX and the low-order 32 bits are in EAX. It works on a single operand that can be either in a register or in memory.The DEC instruction is used for decrementing an operand by one.
Figure 1 shows the 32 bits found in an ARM data-processing instruction; each bit has a specific purpose, either individually or as part of a group.
A few weeks ago, I wrote How To Ensure Quality In Chinese Factories By Writing Work Instructions. So, if we need to check whether a number in a register is even or odd, we can also do this using the TEST instruction without changing the original number.The NOT instruction implements the bitwise NOT operation. First of all, what does term \"inline\" mean? Now, it's easier to guess about inline assembly. The XOR operation sets the resultant bit to 1, if and only if the bits from the operands are different. For example −The AND operation can be used for clearing one or more bits. If this is 1, the number is odd, else the number is even.Assuming the number is in AL register, we can write −When the above code is compiled and executed, it produces the following result −Change the value in the ax register with an odd digit, like −Similarly to clear the entire register you can AND it with 00H. MASM uses the standard Intel syntax for writing x86 assembly code. For years, PC programmers used x86 assembly to write performance-critical code. If you are interested in good factory management, you should probably go have a look at them.). A broader goal of our work is to understand how humans produce and use visual instructions. After division, the 32-bit quotient goes to the EAX register and the 32-bit remainder goes to the EDX register.When the above code is compiled and executed, it produces the following result − Following section explains MUL instructions with three different cases −The multiplicand is in the AL register, and the multiplier is a byte in the memory or in another register. The product generated is stored in the EDX:EAX registers, i.e., the high order 32 bits gets stored in the EDX register and the low order 32-bits are stored in the EAX register.The following example multiplies 3 with 2, and displays the result −When the above code is compiled and executed, it produces the following result −The DIV (Divide) instruction is used for unsigned data and the IDIV (Integer Divide) is used for signed data.The dividend is in an accumulator. If you want to check whether a given number is odd or even, a simple test would be to check the least significant bit of the number. The MUL (Multiply) instruction handles unsigned data and the IMUL (Integer Multiply) handles signed data. For example, say the BL register contains 0011 1010. For example, let us assume the AL register contains 0011 1010, you need to set the four low-order bits, you can OR it with a value 0000 1111, i.e., FH.The following example demonstrates the OR instruction. The INC instruction is used for incrementing an operand by one.
Instructions are used by the processor—let's take one look at the machine code that the instructions represent.
The bitwise AND operation returns 1, if the matching bits from both the operands are 1, otherwise it returns 0. After division, the 16-bit quotient goes to the AX register and the 16-bit remainder goes to the DX register.The dividend is assumed to be 64 bits long and in the EDX:EAX registers. For example, for an instruction like MUL DX, you must store the multiplier in DX and the multiplicand in AX.The resultant product is a doubleword, which will need two registers.
It works on a single operand that can be either in a register or in memory.The ADD and SUB instructions are used for performing simple addition/subtraction of binary data in byte, word and doubleword size, i.e., for adding or subtracting 8-bit, 16-bit or 32-bit operands, respectively.The ADD and SUB instructions have the following syntax −However, like other instructions, memory-to-memory operations are not possible using ADD/SUB instructions. Let us store the value 5 and 3 in the AL and the BL registers, respectively, then the instruction,When the above code is compiled and executed, it produces the following result −The XOR instruction implements the bitwise XOR operation.
(By the way, we have recently published a number of resources on the CMC website. If you need to clear the high-order bits to zero, you AND it with 0FH.Let's take up another example.