Summarizing the ARM for x86 Programmers


I Am, Therefore I Think

RISC: The ARM architecture is RISC -based, yielding two facts of life: an instruction set that’s easy to decode, at the cost of memory accesses that aren’t atomic. While Intel’s more complex x86 architecture lets the programmer increment a memory location with a single machine instruction, ARM requires three explicit steps instead: load-to-register, increment-register, store-from-register. The load-store approach puts the burden on the programmer, rather than the CPU, to accomplish the same result, but the power savings is why ARM is the CPU of choice for battery-powered embedded devices like cell phones.

Predication: ARM instructions typically contain “1110” (hex E) in their highest bits, meaning the instructions always execute, but other combinations of high bits indicate conditional execution. For example, high bits of “0000” mean an instruction will execute only if the Zero flag is set, if for example a downward counter just reached zero, or a comparison between two…

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A Month With Raspbian


I Am, Therefore I Think

Three months on, my Raspberry Pi is still proving a delight. I have settled on the Raspbian distribution as my tinkerer’s habitat, giving me access to the floating-point unit in the glibc libraries (especially libm.so).

However, being mostly uninitiated in Debian administration, I have spent some time learning “the Debian way” of doing things. This article will therefore be a shameless hodge-podge of Raspbian review and Debian ignorance, plus a handy (for me) trick at the end.

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Κρυπτογράφηση Δεδομένων – Τι είναι και Πώς Λειτουργεί


Σε έναν κόσμο χωρίς κρυπτογράφηση δεδομένων, θα ήταν αδύνατον να έχουμε ένα προσωπικό email, έναν προσωπικό λογαριασμό στο facebook, ή να χρησιμοποιήσουμε την πιστωτική για αγορές στο Internet. Η κρυπτογράφηση δεδομένων χρησιμοποιείται παντού, και είναι η “κλειδαριά” που κρατάει την ψηφιακή μας ζωή ασφαλή. Ας δούμε πώς λειτουργεί.

 

κρυπτογράφηση δεδομένων τι είναι πώς λειτουργεί