Gandalf61 mentions here that there are opcodes that "load the next word into Register A", treat the bits at the next address defined by program counter as data and loads this data. I am interested in examples of computers and CPUs that have such as opcode.
Context: Learning basic computer architecture, and interested in how to load constants into registers. In nandgame.com and "nand to Tetris" course (that uses "hack computer" and "hack assembly"), there is "a-instruction", specified by 15th bit set to 0, that treats the instruction as 15 bits of data. With "load immediate" instruction (or similar name) in a few real-world CPUs I read about, a few bits will be treated as data and loaded into register. I am interested overall in how a constant defined in assembly or in a program gets into the CPU. Have not seen any that worked like Gandalf61 mentioned, therefore asking.