The opinion of the Court was delivered by
CLIFFORD, J.Defendant was sentenced to a custodial term on his criminal convictions. He served part of that term, after which the sentence was suspended and he was placed on probation. When defendant violated the terms of his probation, the trial court sentenced him to a custodial term exceeding that originally imposed for the underlying offense. On appeal defendant challenged that sentence on double jeopardy grounds. The Appellate Division affirmed the sentence, State v. Ryan, 171 NJ.Super. 427 (1979). We granted certification, 82 N.J. 297 (1980), to review that determination as well as the Appellate Division’s decisions denying sentence credit for time spent on probation and interpreting the impact of N.J.S.A. 2A:168-4 on R. 3:21-10(b) proceedings.
I
In January 1974 defendant, Edward Joseph Ryan, pleaded guilty to charges of larceny and breaking and entry with intent to steal. He was sentenced to concurrent terms of three to five years in New Jersey State Prison. After serving approximately six months in custody defendant moved for sentence modification under that provision of R. 3:21-10(b) permitting “entry of the defendant into a custodial or non-custodial treatment or rehabilitation program for drug or alcohol abuse * * The original sentencing court granted the motion effective August 1, 1974. It transferred defendant to Patrick House, a *4narcotic treatment facility of Jersey City Medical Center and placed him on probation for two years.1
In February 1977 Ryan was cited for violating the conditions of his probation. He pleaded guilty to absconding from probationary supervision and leaving the state without permission. It further developed at a hearing on those charges that seven detainers had been lodged against defendant; the State of New York was attempting to extradite him; he was serving thirty days on a conviction for malicious damage and larceny; and he was facing additional punishment for a contempt of court conviction.
Confronted with this supplemental information the trial court revoked both the probation and the suspension of the original three to five year sentence, and sentenced defendant to concurrent terms of five to seven years, the statutory maximum for the underlying offenses. On appeal to the Appellate Division defendant challenged that sentence as violating his double jeopardy rights on the ground that his original sentence was impermissibly increased after having been partially executed. Ryan further claimed entitlement to sentence credit for the time he had spent in the program prior to reincarceration. In addition, he contested the trial court’s power to invoke the provision of N.J.S.A. 2A:168-4 allowing imposition of a custodial term after revocation of probation, claiming that the statute is inapplicable in the context of R. 3:21-10(b) sentence modifications.
*5In rejecting these contentions the Appellate Division relied on the language of N.J.S.A. 2A:168-4 authorizing “the imposition of any sentence that could have been imposed for the underlying crime after probation violation has occurred.” 171 N.J.Super. at 434. Hence the court below approved the sentence of five to seven years after probation violation, even though the original sentence had aggregated three to five years and had been partially served. For its conclusion it relied heavily on State v. Cunningham, 143 N.J.Super. 415 (App.Div.1976), which in similar circumstances upheld the imposition of a higher sentence after violation of probation. 171 N.J.Super. at 432.
In disposing of defendant’s contention that he was entitled to sentence credit for time spent on probation, the Appellate Division stressed the substantive differences between a probationer’s condition of relative freedom of movement and a custodial prisoner’s confinement. It concluded that the statutory scheme and prevailing case law recognize those differences in declining to equate probation and prison time. Id. at 441-43. See State v. Smeen, 147 N.J.Super. 229, 233-34 (App.Div.), certif. den., 74 N.J. 263 (1977). See also Hall v. Bostic, 529 F.2d 990, 991 (4th Cir. 1975), cert, den., 425 U.S. 594, 96 S.Ct. 1733, 48 L.Ed.2d 199 (1976) (“There is nothing unusual in the denial * * * of credit for probation or parole time against a prison sentence. It is common to both state and federal probation and parole systems. The validity of such denial has been universally recognized both in federal and state decisions” (footnote omitted).). However, in denying sentence credit for probation time, the court below did so without prejudice to defendant’s right to move in the trial court for credit limited to the time he had spent at Patrick House, inasmuch as the record was uninformative as to “the extent to which defendant’s liberty had been restrained during the two months or so he had spent there.” 171 N.J.Super. at 442.
Finally, the Appellate Division refused to adopt defendant’s position that the provision of N.J.S.A. 2A: 168-4, which empowers the trial court, after revocation of probation, to “impose any *6sentence which might ordinarily have been imposed” does not apply to probationary terms meted out in connection with R. 3:21-10(b) modifications. The court held that the application of the statute to such probation terms was manifestly in keeping with the legislative mandate, N.J.S.A. 2A:168-1 and N.J.S.A. 2A:164-17, as well as the case law on the subject. See, e. g., State v. Johnson, 133 N.J.Super. 457 (App.Div.1975).
On these latter two issues, namely, the disallowance of sentence credit for time spent on probation, at least under the circumstances of this case, and the applicability of N.J.S.A. 2A:168-4 to modification of sentence proceedings under R. 3:21-10(b), we are in accord with the Appellate Division’s disposition and generally adopt its reasoning.2 Our opinion in State v. Williams, 81 N.J. 498 (1980), filed after the Appellate Division decision in this case was handed down, is scant support for defendant’s sentence credit argument. • The underpinning of the credit allowance for time spent on probation in Williams was the evident unfairness of denying credit inasmuch as uninterrupted service of defendant’s sentence was rendered impossible only through the trial court’s error in granting probation. 81 N.J. at 500. See also State v. Braeunig, 135 NJ.Super. 89, 94 (Law Div. 1975), mod. on other grounds, 140 N.J.Super. 245 (App.Div.1976).
However, because we disagree with the Appellate Division’s resolution of defendant’s double jeopardy argument, we reverse the judgment below and reinstate the original three-to-five year aggregate custodial sentence.3
*7II
Prior to the adoption of the Code of Criminal Justice, resort to the sentencing provision of N.J.S.A. 2A: 168-4 was more frequently found in situations in which, on conviction of the underlying offense, the court had either suspended the imposition of any sentence or had imposed sentence and immediately suspended the execution thereof and had placed the defendant on probation.4 When defendant thereafter violated probation, a number of options were open to the trial court under the statute: it might continue the probation or revoke both the probation and the suspension of any sentence previously imposed; following any such revocation it might require a defendant to serve the sentence originally imposed or it might impose any sentence that could have been meted out originally on conviction of the underlying offense.5
The case law recognizing the applicability of N.J.S.A. 2A: 168-4 in the stated circumstances is clear. See In re White, 18 N.J. 499 (1955); State v. Driesse, 95 N.J.Super. 491 (App.Div. 1967); State v. Zachowski, 53 N.J.Super. 321 (App.Div.1959). Although the statements of principle justifying the imposition *8of a custodial sentence after probation revocation under N.J.S.A. 2A:168-4 have not been entirely consistent, compare State v. Wall, 126 N.J.Super. 594, 596 (App.Div.1976), and State v. Pallitto, 107 N.J.Super. 96,100 (App.Div.1969), certif. den., 55 N.J. 309 (1970), with State v. Pascal, 133 N.J.L. 528, 532-33 (Sup.Ct.1946), aff’d, 1 N.J. 261 (1949), the sentence imposed after revocation of probation should be viewed as focusing on the original offense rather than on the violation of probation as a separate offense. This is borne out by the statute’s limitation on the sentence that follows a violation of probation to the sentence already imposed or one that might originally have been imposed, thereby anchoring the proceedings to the original offense. The custodial term allowed by the statute is imposed because of the defendant’s failure to abide by the conditions of his probation but is not for the violation of those conditions. A respected text offers this exposition of the situation in which a defendant’s entire original sentence was suspended:
In the event the Court finds that the defendant has violated the terms of his probation, the Court may either continue or revoke the original probation and the suspension of sentence. In the event the Court chooses to revoke the original probation, it may then cause the original suspension of sentence to be executed or it may impose any sentence, including the maximum, which might originally have been imposed. Imposing the maximum sentence for the original offense after revocation of probation without grand jury indictment or trial by jury is not unconstitutional, since the new sentence is only a sanction for defendant’s original offense for which he had been properly tried. [R. Knowlton & D. Cobum, New Jersey Criminal Practice, § 24:11 (footnotes omitted).]
That the imposition of a custodial term after revocation of probation does not violate a defendant’s double jeopardy rights is beyond question in view of the Supreme Court’s recent flat statement to that effect in United States v. DiFrancesco, -U.S. -,-, 101 S.Ct. 426, 438, 66 L.Ed.2d 328, 346 (1980): “[Tjhere is no double jeopardy protection against revocation of probation and the imposition of imprisonment.” But that does not answer the question squarely presented here, not addressed by the New Jersey authorities cited above, and apparently left open by the Supreme Court in DiFrancesco, supra, namely, whether double jeopardy considerations militate against *9increasing the defendant’s prison sentence after violation of probation when he has already served a portion of that custodial term6 That feature of the case is central to Ryan’s position. Simply stated the contention is that jeopardy attached as soon as defendant commenced serving his prison term, hence principles of double jeopardy foreclosed the imposition of any increased term after violation of probation. We agree.
Ill
Out of respect for our dissenting colleague’s view that “application of the reasoning and doctrine in DiFrancesco to the factual pattern of the instant case indicates an absence of a double jeopardy obstacle,” post at 17, we first address that contention directly.
The Supreme Court in DiFrancesco held 18 U.S.C. § 3576, which authorizes the prosecutor to appeal the imposition of sentence on a defendant who qualified as a “dangerous special offender.” It ruled that such an appeal does not violate the Double Jeopardy protection against double punishment. DiFrancesco, -U.S. at-, 101 S.Ct. at 438, 66 L.Ed.2d at 347. That case is distinguishable from the present one.
The issue in DiFrancesco was stated in this fashion: “[o]ur task is to determine whether a criminal sentence, once pronounced, is to be accorded constitutional finality and conclusiveness similar to that which attached to a jury’s verdict of acquittal.” Id. at -, 101 S.Ct. at 435, 66 L.Ed.2d at 343 *10(emphasis added). The instant case is concerned with whether a criminal sentence is entitled to finality once the defendant has begun to serve it. Our holding is that in the latter circumstances, jeopardy attaches once the defendant has commenced serving his prison term.
The distinction between this case' and DiFrancesco is further highlighted by the expectation analysis offered in the latter case. Since the defendant in DiFrancesco had been tried as a dangerous special offender under 18 U.S.C. §§ 3575 and 3576, the Supreme Court noted that he had no legitimate expectation of finality in his original sentence. The statute gave him notice of the possible appeal. Id. at-, 101 S.Ct. at 438, 66 L.Ed.2d at 347. In the case now before us the defendant had no reason to expect that his original sentence was not final at the time it was imposed and his imprisonment began. When he subsequently moved for sentence modification under R. 3:21-10(b), the defendant was seeking special, more lenient treatment subject to certain conditions. Thus, the defendant was on notice that a “breach of those conditions may result in revocation of the beneficial treatment”, but given the finality of his original sentence, he would expect “at the very worst [that] the original sentence may be reinstated.” Id. at-, 101 S.Ct. at 443, 66 L.Ed.2d at 353 (Brennan, J., dissenting).
It is unmistakably clear that the Supreme Court, in DiFrancesco, did not intend to overrule the long-standing principle that one of the purposes of the guarantee against double jeopardy is to protect a criminal defendant against double jeopardy is to protect a criminal defendant against the imposition of more than one punishment for a single offense. Id. at -, 101 S.Ct. at 437-438, 66 L.Ed.2d at 346-47. See Whalen v. United States, 445 U.S. 684, 688, 100 S.Ct. 1432, 1436, 63 L.Ed.2d 715, 721 (1980); North Carolina v. Pearce, 395 U.S. 711, 717, 89 S.Ct. 2072, 2076, 23 L.Ed.2d 656, 664-65 (1969). In that connection this Court has recognized that jeopardy attaches as soon as execution of the sentence commences. State v. Laird, 25 N.J. 298, 306-07 (1957). We have likewise acknowledged the princi*11pie that once a sentence has gone into operation, “serious double jeopardy problems” would arise if the trial judge were permitted to increase that sentence. State v. Matlack, 49 N.J. 491, 501 (1967); see State v. Vaccaro, 150 N.J.Super. 410, 413 (App.Div. 1977). Those problems are squarely presented here.
The Appellate Division looked to State v. Cunningham, supra, for authority in upholding the imposition of the increased sentence in this case. It sought support as well from North Carolina v. Pearce, supra, for its analogy to cases where a conviction is reversed on appeal, the original sentence vacated, and a more serve penalty imposed following retrial. Finally, in affirming the longer prison term imposed on Ryan the Appellate Division rejected defendant’s argument that his resentencing should be governed by the provisions of N.J.S.A. 2A:164-16, covering split sentences to county institutions. The court found this case controlled by N.J.S.A. 2A:164-17, requiring all except life sentences to be for a maximum and minimum term. 171 N.J.Super. at 438. This last point need not detain us as we are in accord with the Appellate Division’s view of it.
State v. Cunningham, supra, cannot be distinguished in any significant respect from the case before us. In Cunningham defendant was convicted of possession of a controlled dangerous substance and sentenced to a prison term of two to three years. After serving some four months of the term he sought sentence reconsideration under R. 3:21-10. In granting the application the trial court suspended execution of the unserved balance of the prison sentence and placed defendant on probation for three years, with a special condition that he enter and successfully complete a specified drug rehabilitation program. Defendant violated his probation by leaving the program without consent of the staff, whereupon the court revoked his probation and sentenced him to three to four years in prison pursuant to N.J.S.A. 2A:168-4. Defendant’s motion for postconviction relief was denied and the Appellate Division affirmed, holding that the imposition of the longer prison sentence did not violate defendant’s double jeopardy rights.
*12Cunningham is based on two propositions, neither of which is persuasive. First, even though double jeopardy attaches when execution of a sentence commences, the increased term after violation of probation “is imposed for violation of probation, caused by defendant’s subsequent act, and is not a second or additional punishment for the original crime,” 143 N.J.Super. at 417. We have rejected this notion, supra at 7-8. Second, Cunningham warns that “a contrary ruling * * * would undoubtedly have a chilling effect on the sentencing judge’s willingness to reconsider a sentence and place a defendant on probation, with or without special conditions.” Id. at 418. We do not share this apprehension.
To be sure, whenever a sentencing judge must decide whether to permit an inmate to leave the prison walls for entry into a drug rehabilitation program, the decision poses a risk. The same risk is inherent in suspending the imposition of any sentence or in sentencing the offender to probation pursuant to N.J.S.A. 2C:45-1. But the sentencing discretion can be exercised in the case of a particular offender who has served a portion of his custodial term as well as it can in the case of one who has violated the terms accompanying his suspension or probation. We acknowledge the absence of perfect symmetry between the first situation, in which the defendant can be returned to confinement only for the balance of his previously imposed sentence, and the second, where the defendant faces the maximum term that could be imposed for the offense of which he was convicted. These are appropriate matters for consideration by the court faced with a motion for modification of sentence under R. 3:21-10.7 If, under the circumstances of this case and Cunningham, the court’s exercise of discretion is “chilled” by the prospect that a probation violator will be exposed to no more than the unserved balance of his term — a *13prospect we deem unlikely — that is simply the price of vindication of a defendant’s right not to put in double jeopardy. As our decision indicates, we disapprove of State v. Cunningham, supra, and that case may no longer be considered as acceptable authority.
Finally, we address the State’s contention, adopted by the Appellate Division, that when a defendant by his own motion has his original sentence set aside, the constitutional guarantee against double jeopardy does not restrict the imposition of whatever sentence may be legally authorized, even though it may be greater than the original sentence imposed. On the strength of North Carolina v. Pearce, supra, the court below attempted to apply to the instant matter the principal derived from that case that a more severe sentence upon reconviction is permitted when justified by defendant’s subsequent conduct, absent any motive of retaliation for the taking of an appeal. See Pearce, supra, 395 U.S. at 723-26, 89 S.Ct. at 2079-81, 23 L.Ed.2d at 668-70. Proceeding by way of analogy the Appellate Division concluded that “a sentence imposed after probation has been violated can reflect the added basis for evaluating defendant’s amenability to reform, namely, his response to probation.” 171 N.J.Super. at 436.
There can be no doubt that defendant’s subsequent conduct is an appropriate concern at the time of sentencing after reconviction. But the linchpin of Pearce’s analysis is the premise that
the original conviction has, at the defendant’s behest, been wholly nullified and the slate wiped clean. * * * [S]o far as the conviction itself goes, and that part of the sentence that has not yet been served, it is no more than a simple statement of fact'to say that the slate has been wiped clean. The conviction has been set aside, and the unexpired portion of the original sentence will never be served. [395 U.S. at 721, [89 S.Ct. at 2078], 23 L.Ed.2d at 667 (emphasis in original).]
Here, Ryan has not attacked his original conviction. His R. 3:21-10(b) motion sought only a modification of sentence, not a new trial. The granting of that motion resulted only in a suspension of the execution of his original sentence pending successful completion of the drug rehabilitation program and *14probationary term, not in a vacation or annulment of that sentence. In effect the sentence became temporarily and conditionally inoperative. Under the circumstances there was no impairment of the jeopardy that attached at the execution of the sentence. The slate was not “wiped clean” within the meaning of Pearce.
IV
The sentence imposed following defendant’s violation of probation is vacated and the original sentence aggregating three to five years is reinstated. The judgment of the Appellate Division is:
Reversed.
So much of the transcript on the motion hearing as has been furnished to us contains no warning by the court to defendant concerning the consequences of probation violation. Ryan signed a standard form of the probation department, informing him that “[i]f you fail to observe the conditions of your probation you may be returned to court and required to serve your sentence in an institution” (emphasis supplied). No mention was made of the possibility of any increase in the term that had previously been imposed. Henceforth, in similar circumstances the court should spell out in unmistakable terms precisely what penalties may await a defendant who does not adhere to the conditions of his probation. See also R. 3:21-7.
Our discussion of the applicability of N.J.S.A. 2A: 168-4 to R. 3:21-10(b) proceedings would not be different had this case arisen under the parallel provision of the New Jersey Code of Criminal Justice, generally effective September 1, 1979. N.J.S.A. 2C:45-3(b) in its amended form reads as follows:
When the court revokes a suspension or probation, it may impose on the defendant any sentence that might have been imposed originally for the offense of which he was convicted.
Even though defendant was paroled prior to the time his appeal was heard in the Appellate Division, the question of appropriate sentence following *7violation of probation is not moot. The duration of his parole is limited by “the term specified in the original sentence.” N.J.S.A. 30:4-123.65. Should defendant’s parole be revoked and he be recommitted, “the term of further imprisonment upon such recommitment * * * shall not exceed the original sentence determined from the date of conviction.” N.J.S.A. 2C:43-9(b).
Under the Code of Criminal Justice it is no longer necessary for the sentencing court to impose and suspend the execution of a sentence before placing a defendant on probation. Rather, the Legislature now treats probation as a sentence in and of itself, hence the statutory reference to a court that “sentences [an offender] to be placed on probation.” N.J.S.A. 2C:45-l(a). Furthermore, probation is properly viewed as a conditional sentence in that the defendant remains subject to a prison term for failure to comply with the conditions imposed by the court. See N.J.S.A. 2C:45-3(a)(4) and ABA Standards, Probation § 1.1(b) and Commentary (Approved Draft, 1970).
For a discussion of the philosophy of probation and its role in our criminal jurisprudence one may profitably consult Justice Jacobs’ opinion for the court in Adamo v. McCorkle, 13 N.J. 561, 563-67 (1953).
In DiFrancesco the Supreme Court, after reviewing the common law double jeopardy principles, pointed out:
[Ojur Double Jeopardy clause was drafted with the common law protections in mind. This accounts for the established practice in the federal courts that the sentencing judge may recall the defendant and increase his sentence, at least (and we venture no comment as to this limitation) so long as he has not yet begun to serve that sentence. [United States v. DiFrancesco, supra,- U.S. at -, 101 S.Ct. at 435, 66 L.Ed.2d at 344 (citations omitted) (emphasis added).]
For example, one might reasonably expect that the experience of a defendant who has spent some time behind bars and had a taste of prison life might provide a greater deterrent to violation of probation.