MBASIC: differenze tra le versioni

Versione delle 09:56, 24 set 2011

Versione delle 10:42, 24 set 2011

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==Caratteristiche tecniche==

===Interazione con il sistema===

L'MBASIC versione 5 richiedeva un sistema CP/M con almeno 2 8 [[byte|kB]] di memoria [[Random Access Memory|RAM]] libera ed almeno un'[[floppy disk drive|unità floppy]]. A differenza del BASIC-80, la versione per computer con [[CPU]] [[Intel 8080|8080]]/[[Zilog Z80|Z80]] dell'[[Altair BASIC]] che Microsoft distribuiva personalizzato per lo specifico [[hardware]] del sistema su cui doveva poi girare, l'MBASIC si appoggiava direttamente al sistema CP/M, sfruttandone le chiamate di sistema per la gestione delle operazioni di [[input/output]], ed era in questo modo indipendente dall'hardware sottostante. L'MBASIC non usava tutti i servizi del CP/M ma solo la [[terminale (informatica)|console]], la gestione della stampante e l'accesso ai [[floppy disk|floppy]].

L'MBASIC non usava tutti i servizi del CP/M ma solo la [[terminale (informatica)|console]], la gestione della stampante e l'accesso ai [[floppy disk|floppy]]: il linguaggio non supportava la modalità [[Computer grafica|grafica]], i colori, i [[joystick]], il [[mouse]], le [[Local Area Network|reti locali]], il suono o gli [[Real-time clock|orologi in tempo reale]]. Inoltre l'MBASIC non supportava le aree utente messe a disposizione del CP/M per l'organizzazione dei file sul disco. Siccome il CP/M era un sistema pensato per computer mono-utente, anche l'MBASIC non supportava nessuna forma di [[multitasking]] come ad esempio il blocco dei file. Nonostante queste limitazioni, l'MBASIC era considerato comunque un BASIC potente e funzionale.

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===Struttura del linguaggio===

MBASIC in the uncustomized form had no functions for [[Computer graphics|graphics]], color, joysticks, mice, [[serial port|serial communications]], [[Ethernet|networking]], sound, or even a real-time clock function. MBASIC did not fully support the features of the host CP/M operating system, for example, it did not support CP/M's user areas for organizing files on a diskette. Since CP/M systems were typically single-user and stand alone, there was no provision for file or record locking, or any form of [[computer multitasking|multitasking]]. Apart from these limitations, MBASIC was considered at the time to be a powerful and useful implementation of BASIC.

L'MBASIC è un [[linguaggio interpretato]]: il [[codice sorgente]] viene salvato in memoria

== Features ==

=== Language system ===

MBASIC is an [[Interpreter (computing)|interpreter]]. Program source text was stored in memory in [[bytecode|tokenized]] form, with BASIC keywords replaced by one-byte tokens which saved memory space and speeded execution. Any line prefixed with a line number was stored as program text; BASIC statements not prefixed with a line number were executed immediately as commands. Programs could be listed on the screen for editing, or saved to disk in either a compressed binary format or as plain [[ASCII]] text. Every source line was identified with a number, which could be used as the target of a [[GOTO]] or [[GOSUB]] transfer. Only line editing commands were provided. <ref> CP/M products providing full-screen editing support required their own installation routines to customize the software for the specific [[computer terminal]] used as the system console. No support was provided within CP/M to standardize terminal capabilities. </ref> It was often beneficial to save a program as plain text and edit it with a full featured editor.