First recognized byte alignment

Today, when I was writing a program, I encountered a small problem. How can I record the expression of actions on 64 devices? I thought of a resource-saving bit domain, write down the following Program (in 32-bit PC) [cpp] typedef struct {unsigned f1: 1;} new_log_t; typedef struct {unsigned f1: 1;} new_log_t; sizeof (new_log_t) = 4, doesn't it seem to save resources? Try [cpp] typedef struct {unsigned f1: 1; unsigned f2: 1; unsigned f3: 1; unsigned f4: 1; unsigned f5: 1; unsigned f6: 1; unsigned f7: 1; unsigned f8: 1;} new_log_t; typedef struct {unsigned f1: 1; unsigned f2: 1; unsigned f3: 1; unsigned f4: 1; unsigned f5: 1; unsigned f6: 1; unsigned f7: 1; unsigned f8: 1;} new_log_t; sizeof (new_log_t) = 4, what does it seem to know, try [cpp] typedef struct {unsigned f1: 1; unsigned f2: 1; unsigned f3: 1; unsigned f4: 1; unsigned f5: 1; unsigned f6: 1; unsigned f7: 1; unsigned f8: 1; unsigned f9: 1; unsigned f10: 1; unsigned f11: 1; unsigned f12: 1; unsigned f13: 1; unsigned f14: 1; unsigned f15: 1; unsigned f16: 1; unsigned f17: 1; unsigned f18: 1; unsigned f19: 1; unsigned f20: 1; unsigned f21: 1; unsigned f22: 1; unsigned f23: 1; unsigned f24: 1; unsigned f25: 1; unsigned f26: 1; unsigned f27: 1; unsigned f28: 1; unsigned f29: 1; unsigned f30: 1; unsigned f31: 1; unsigned f32: 1; unsigned f33: 1;} new_log_t; typedef struct {unsigned f1: 1; unsigned f2: 1; unsigned f3: 1; unsigned f4: 1; unsigned f5: 1; unsigned f6: 1; unsigned f7: 1; unsigned f8: 1; unsigned f9: 1; unsigned f10: 1; unsigned f11: 1; unsigned f12: 1; unsigned f13: 1; unsigned f14: 1; unsigned f15: 1; unsigned f16: 1; unsigned f17: 1; unsigned f18: 1; unsigned f19: 1; unsigned f20: 1; unsigned f21: 1; unsigned f22: 1; unsigned f23: 1; unsigned f24: 1; unsigned f25: 1; unsigned f26: 1; unsigned f27: 1; unsigned f28: 1; unsigned f29: 1; unsigned f30: 1; unsigned f31: 1; unsigned f32: 1; unsigned f33: 1;} new_log_t; sizeof (new_log_t) = 8, take a look at the total number of 32 Members. [cpp] typedef struct {unsigned f1: 1; unsigned f2: 1; unsigned f3: 1; unsigned f4: 1; unsigned f5: 1; unsigned f6: 1; unsigned f7: 1; unsigned f8: 1; unsigned f9: 1; unsigned f10: 1; unsigned f11: 1; unsigned f12: 1; unsigned f13: 1; unsigned f14: 1; unsigned f15: 1; unsigned f16: 1; unsigned f17: 1; unsigned f18: 1; unsigned f19: 1; unsigned f20: 1; unsigned f21: 1; unsigned f22: 1; unsigned f23: 1; unsigned f24: 1; unsigned f25: 1; unsigned f26: 1; unsigned f27: 1; unsigned f28: 1; unsigned f29: 1; unsigned f30: 1; unsigned f31: 1; unsigned f32: 1;} new_log_t; typedef struct {unsigned f1: 1; unsigned f2: 1; unsigned f3: 1; unsigned f4: 1; unsigned f5: 1; unsigned f6: 1; unsigned f7: 1; unsigned f8: 1; unsigned f9: 1; unsigned f10: 1; unsigned f11: 1; unsigned f12: 1; unsigned f13: 1; unsigned f14: 1; unsigned f15: 1; unsigned f16: 1; unsigned f17: 1; unsigned f18: 1; unsigned f19: 1; unsigned f20: 1; unsigned f21: 1; unsigned f22: 1; unsigned f23: 1; unsigned f24: 1; unsigned f25: 1; unsigned f26: 1; unsigned f27: 1; unsigned f28: 1; unsigned f29: 1; unsigned f30: 1; unsigned f31: 1; unsigned f32: 1;} new_log_t; sizeof (new_log_t) = 4, I understand, then [cpp] typedef struct {unsigned f1: 1; unsigned f2: 1; unsigned f3: 1; unsigned f4: 1; unsigned f5: 1; unsigned f6: 1; unsigned f7: 1; unsigned f8: 1; unsigned f9: 1; unsigned f10: 1; unsigned f11: 1; unsigned f12: 1; unsigned f13: 1; unsigned f14: 1; unsigned f15: 1; unsigned f16: 1; unsigned f17: 1; unsigned f18: 1; unsigned f19: 1; unsigned f20: 1; unsigned f21: 1; unsigned f22: 1; unsigned f23: 1; unsigned f24: 1; unsigned f25: 1; unsigned f26: 1; unsigned f27: 1; unsigned f28: 1; unsigned f29: 1; unsigned f30: 1; unsigned f31: 1; unsigned f32: 1; unsigned f33: 1; unsigned f34: 1; unsigned f35: 1; unsigned f36: 1; unsigned f37: 1; unsigned f38: 1; unsigned f39: 1; unsigned f40: 1; unsigned f41: 1; unsigned f42: 1; unsigned f43: 1; unsigned f44: 1; unsigned f45: 1; unsigned f46: 1; unsigned f47: 1; unsigned f48: 1; unsigned f49: 1; unsigned f50: 1; unsigned f51: 1; unsigned f52: 1; unsigned f53: 1; unsigned f54: 1; unsigned f55: 1; unsigned f56: 1; unsigned f57: 1; unsigned f58: 1; unsigned f59: 1; unsigned f60: 1; unsigned f61: 1; unsigned f62: 1; unsigned f63: 1; unsigned f64: 1;} new_log_t; typedef struct {unsigned f1: 1; unsigned f2: 1; unsigned f3: 1; unsigned f4: 1; unsigned f5: 1; unsigned f6: 1; unsigned f7: 1; unsigned f8: 1; unsigned f9: 1; unsigned f10: 1; unsigned f11: 1; unsigned f12: 1; unsigned f13: 1; unsigned f14: 1; unsigned f15: 1; unsigned f16: 1; unsigned f17: 1; unsigned f18: 1; unsigned f19: 1; unsigned f20: 1; unsigned f21: 1; unsigned f22: 1; unsigned f23: 1; unsigned f24: 1; unsigned f25: 1; unsigned f26: 1; unsigned f27: 1; unsigned f28: 1; unsigned f29: 1; unsigned f30: 1; unsigned f31: 1; unsigned f32: 1; unsigned f33: 1; unsigned f34: 1; unsigned f35: 1; unsigned f36: 1; unsigned f37: 1; unsigned f38: 1; unsigned f39: 1; unsigned f40: 1; unsigned f41: 1; unsigned f42: 1; unsigned f43: 1; unsigned f44: 1; unsigned f45: 1; unsigned f46: 1; unsigned f47: 1; unsigned f48: 1; unsigned f49: 1; unsigned f50: 1; unsigned f51: 1; unsigned f52: 1; unsigned f53: 1; unsigned f54: 1; unsigned f55: 1; unsigned f56: 1; unsigned f57: 1; unsigned f58: 1; unsigned f59: 1; unsigned f60: 1; unsigned f61: 1; unsigned f62: 1; unsigned f63: 1; unsigned f64: 1;} new_log_t; I guess the size of sizeof is 8 bytes, after sizeof is 8 bytes, my PC structure is 4 bytes aligned, so how can I make it one byte aligned to meet my requirements to save resources, use the following statement # pragma pack (push, 1) struct {}# pragma pack (pop) example [cpp] # pragma pack (push, 1) // The effect begins with typedef struct {unsigned f1: 1;} new_log_t; # pragma pack (pop) // The effect ends (Other struct not wrapped by this command (at least one member) sizeof is 4) # pragma pack (push, 1) // effect start typedef struct {unsigned f1: 1;} new_log_t; # pragma pack (pop) // The effect ends (the other struct (at least one member) that is not wrapped by this command is sizeof and then 4) sizeof (new_log_t) = 1, it seems that the precision can only be 1 byte. (check whether there is a better way to write it later.) Postscript: I have been listening to the byte alignment before, but I can't hear it, only when you have encountered such problems can you have a deep understanding. By looking at and understanding the needs of those who need it, you can deepen your understanding and get twice the result with half the effort.