Do you know the difference between architecture and operating system?

The term "Architecture", in the context of computers, can refer to several different concepts, including Computer Architecture, Software Architecture, and Instruction Set Architecture. Since your contrasting it with Operating Systems, it seems most likely that you're referring to Instruction Set Architecture.

Instruction Set Architecture (ISA) is an abstract view of the system, including the instruction set, memory address modes, processor registers, and address and data formats. The ISA is closer to the hardware than the Operating System.

Examples of Instruction Set Architectures:

x86 (also known as IA-32) (Pentium, Athlon)

Motorola 68k

Alpha AXP (DEC Alpha)

ARM (Acorn RISC Machine)

System/360

An Operating System is the set of computer programs that manage the hardware and software resources of a computer. The OS is at a higher level of abstraction than the ISA, and would be considered closer to the user.

Examples of Operating Systems:

Microsoft Windows

UNIX

Mac OS (pre-OSX, OSX is a UNIX variant)

AmigaOS

BeOS